Wind Turbine Blade Decommissioning in Brazil: The Economic Performance of Energy Recovery in a Cement Kiln Compared to Industrial Landfill Site

Abstract

This study compares the logistics of decommissioning wind turbine blades for energy recovery in a cement kiln (proposed scenario) to industrial landfill site disposal and coke fuel in a cement kiln combined (base scenario) to check the financial cost of the operation in each scenario. The wind farm coordinates, wind turbine blade mass, and logistics costs of the 760 wind farms in Northeast Brazil were used to determine the location of a material processing center (MPC) for wind turbine blade waste. The findings showed that the cost of the proposed scenario was higher than that of the base scenario when a single MPC was considered to serve the Northeast region. However, the proposed scenario was preferable when installing decentralized MPCs to serve the Northeast region. The installation of four additional decentralized MPCs shows that energy recovery is a more favorable technological route in the economic performance for disposing of 96% of the wind turbine blades in operation in the Northeast region, which represents 210,188 tonnes. Therefore, the gradual implementation of MPCs should consider a wind turbine blade decommissioning plan to support the energy recovery potential.

1. Introduction

Brazilian wind sources, especially in the Northeast region of the country, have shown promising potential for the expansion of wind power generation. In 2021, 11% of all electricity generation injected into the National Interconnected System (SIN) came from wind [1], with 20% of the country supplied by wind turbines at peak [2]. The Ten-Year Energy Expansion Plan estimates that the installed wind power capacity in Brazil should increase by 55% by 2031 [3]. By 2030, the cost of wind energy is expected to fall by up to 55% compared to 2018 [4]. In addition, the historical average capacity factor for onshore wind power plants in Brazil was 43% during the period 2018–2022, which is higher than the world average of 36% [5]. Therefore, wind power is strategic for the expansion of the Brazilian electricity mix in the coming years.

The first wind turbine in Brazil was implemented in June 1992 in Fernando de Noronha with an installed capacity of 75 kW. In 1994, the Morro do Camelinho wind farm with an installed capacity of 1000 kW was the first wind farm to be implemented in the country [6]. The useful life of wind turbines is 20 years [7,8]; therefore, the first wind turbines installed in Brazil have reached the end of their useful life. By 2030, more than 50 wind farms will have reached their 20-year operating life, constituting more than 600 wind turbines and 940 MW of power [8], representing approx. 9700 tonnes of decommissioned blade, which will require an environmentally appropriate destination. For the following years, an average growth rate of 30% per year of decommissioned wind turbine blade waste is expected, surpassing 200,000 tonnes of accumulated waste by 2042. After the operation period defined in the contract with the proof that each of the maintenance steps was carried out, it is recommended that a technical assessment of the wind turbines and the remaining components is carried out to decide on the procedure to be adopted, such as useful life expansion, repowering, or decommissioning [8].

Wind farm parts are made of materials with high recycling rates, such as the tower, foundation, generator, and gearbox [9]. Estimates are that 80% to 90% of the steel and cast iron can be recycled and this rate reaches 95% for aluminum and copper. The steel towers, made up of only one material, are 98% recyclable. The reinforced concrete towers, on the other hand, can have different destinations: processing to separate steel and concrete (in which both can be recycled), use of granular concrete in roads and constructions, or final disposal in a landfill [8].

Wind turbine blades, which are mostly made of glass-fiber-reinforced polymer (GRP) materials such polymers reinforced as thermosetting with glass or carbon fibers, show a low recycling rate due to the complex material composition [9], which results in a high recycling cost [10]. Fluidized bed and pyrolysis allow for the recovery of fibers, fillers, and energy at a process cost of USD 305 per tonne using electricity, incineration a cost of USD 180 per tonne, and grinding a cost of USD 94 per tonne [11], which could compete with energy recovery in a cement kiln, particularly when considering a multifunctional scenario, which serves for material disposal and energy supply to replace the acquisition of petroleum coke at a price of USD 128.5 per tonne [12]. Research and development (R&D) efforts focus on processes to recover the fibers and polymer matrix or to shred the GRP for use in new polymer composites and concrete [13].

GRPs with a higher recyclability are mainly modified thermoset composites with active covalent bonding in epoxy resin, thermoplastic composites with a low viscosity such as anionic polylactam-12 (APLC-12), cyclic butylene terephthalate (CBT), and composites with jute, kenaf, flax, coconut, and bamboo vegetable fiber [10]. A new generation of hardeners, such as Recyclamine^® launched by Connora Technologies, supports the development of thermosets that can be converted into recyclable material such as thermoplastics [9]. Recyclamine^® hardeners have terminal amino groups linked by a central group, which is where the cleavage of cured epoxy cross-links is achieved from the combination of temperature (70–100 °C) and pH (acid) [14]. In this context, one company has launched the RecyclableBlade^® on the market, which is a wind turbine blade with a resin that simplifies its separation from the other components of the blade at the end of its useful life, increasing the recycling potential of the composite materials [15]. The development of recyclable wind turbine blades favors new wind farms; however, components that are in full operation or have been decommissioned in recent years in Brazil require environmentally appropriate disposal.

GRP recycling has technical and economic limitations that make large-scale implementation unfeasible in the short term. Mechanical GRP recycling affects the fiber properties, which limits the recovery of long fiber [16]. Chemical GRP recycling by pyrolysis is not yet economically viable and requires high energy consumption, while processes such as a fluidized bed process, microwave-assisted pyrolysis, solvolysis, and high-voltage fragmentation are only available on a laboratory scale [16,17,18]. GRP energy recovery through co-processing in cement kilns has been used in Europe and has the advantages of scalability and low waste generation. In addition, GRP energy recovery is at the highest technological readiness level (TRL 9), which indicates that this technology has already been implemented and has proven to be effective [17].

Globally, the most common route for disposing of polymers and their derived materials is by sending them to industrial landfill sites and 90% of GRP is landfilled [18]. GRP disposal in industrial landfill sites causes environmental and health problems due to the emission of various toxic additives and by-products of the decomposition of the polymer matrix, such as methane and other volatile organic compounds [19,20]. GRP disposal in large pieces is not an option in the European Union and will be banned in more countries in the near future due to stricter environmental regulations [21].

The cement industry is currently faced with the great challenge of reducing its vast carbon footprint toward sustainability [22]. Cement emits large amounts of CO₂ during its production, the decomposition of limestone releases a large proportion of CO₂ in cement production, and the use of fossil fuels in calcination also contributes to CO₂ emissions [23]. For this reason, it is urgent to develop cleaner ways to produce cement with a low carbon footprint [24]. Researchers are currently concentrating on designing and producing low-carbon cement, substituting cement with other supplementary cementitious materials to reduce CO₂ emissions [25] or reduce the carbon footprint during the manufacturing stage at cement plants. In recent years, due to increasing environmental and energy worries, the use of industrial wastes for cement production has gradually gained worldwide attention [26]. Therefore, energy recovery from solids, which is practiced throughout Europe as a substitute for fossil fuels in cement and energy industries [27], is an attractive option for disposing of GRP in the short term.

The aim of this work is to assess the economic viability of the logistics of decommissioning 1 tonne of wind turbine blades for energy recovery in a cement kiln to replace coke fuel (proposed scenario) compared to industrial landfill site and coke fuel in a cement kiln combined (base scenario). To this end, a centralized and four additional decentralized material processing centers (MPCs) were proposed for decommissioned wind turbine blades in northeastern Brazil, based on the center of gravity (CG) method, for subsequent material transport for co-processing in the proposed scenario compared to the base scenario. The novelty of this work is the combination of a logistics and economic analysis to support decision making for resource recovery from the decommissioned wind turbine blades in the Brazilian context.

2. Materials and Methods

The methodological procedure steps used for this study are shown in Figure 1.

2.1. Wind Farms Identification

Wind farms in operation were identified by consulting the National Electric Energy Agency’s Generation Information System (SIGA) for the 2022 base year [28]. Regarding the decommissioned wind farms, data from the Atlas de Energia Elétrica do Brasil [6]—which identifies the first wind farms installed in the country—were compared to the recent data from SIGA. The installed wind capacity distribution in Brazil is 91% in the Northeast, followed by 8.9% in the South, and 0.1% in the Southeast. This study only considers wind farms installed in the Northeast of the country to determine the MPC location due to the greater contribution of this region. Wind farms that have not yet started operating were disregarded in this study.

2.2. Useful Life Estimation

The remaining useful life of the wind turbine blades was calculated considering the start-up date of each wind farm and a useful life of 20 years for each project [7,8].

2.3. Wind Turbine Blade Mass Estimation

The wind turbine blade mass estimation considered the onshore installed capacity of 21,155 MW in the 2022 base year [28] with 9.57 tonnes of composite material (fiberglass fabric and epoxy resin) per megawatt installed on average [29]. It was considered that each wind turbine blade is composed of fiberglass fabric (60.4%), epoxy resin (32.3%), balsa wood (2.3%), metal material (1.4%), polyurethane foam (1.7%), protective coating (1.6%), and adhesive (0.3%) on a mass basis [30]. In this regard, the wind turbine blade mass was 10.32 tonnes per megawatt installed on average. It was also considered that wind turbine blades are reduced to sizes of 1.5 m² after decommissioning at the collection site to simplify the transport [27,31] using a wet saw with a diamond wire to minimize dust and debris. The cut wind turbine blades are then loaded onto the trucks to be transported to the MPC [32,33].

2.4. MPC Coordinate Definition

The CG coordinates were defined with the Equations (1) and (2) obtained from Martins and Laugeni [34], which were used by several authors to define the location of activities [35,36,37]:

$$x≔{\displaystyle \frac{\sum (Mi\times xi)}{\sum \left(Mi\right)}}$$

(1)

$$y≔{\displaystyle \frac{\sum (Mi\times yi)}{\sum \left(Mi\right)}}$$

(2)

where the following definitions hold:

$Mi$ represents the mass of wind turbine blades (t) to be transported from a wind farm $i$;

$xi$ represents the coordinate of the wind farm $i$ in the $x$ direction ($\mathrm{k}\mathrm{m}$);$yi$ represents the coordinate of the wind farm $i$ in the $y$ direction ($\mathrm{k}\mathrm{m}$).

The $xi$ and $yi$ coordinates were defined from the available latitude ($xi$) and longitude ($yi$) data for the SIGA wind farms [28]. The location of the MPC was defined based on the amount of blade waste projected for the next 20 years. Using the $x$ and $y$ coordinates of the CG on Google Maps^®, the municipality for implementing the MPC was identified.

2.5. Calculation Economic Viability Assessment

The total financial cost estimation per evaluated scenario used Equations (3) and (4):

$$\mathit{C}\mathit{b}\mathit{a}\mathit{s}\mathit{e}:=Clandfill+Ccoke$$

(3)

$$\mathit{C}\mathit{p}\mathit{r}\mathit{o}\mathit{p}\mathit{o}\mathit{s}\mathit{e}\mathit{d}:=Crecovery$$

(4)

where the following definitions hold:

$\mathit{C}\mathit{b}\mathit{a}\mathit{s}\mathit{e}$ represents the total cost for the base scenario (USD);

$\mathit{C}\mathit{p}\mathit{r}\mathit{o}\mathit{p}\mathit{o}\mathit{s}\mathit{e}\mathit{d}$ represents the total cost for the proposed scenario (USD).

To be economically viable, the proposed scenario must meet Equation (5), which is detailed in Equations (6)–(8):

$$\mathit{C}\mathit{r}\mathit{e}\mathit{c}\mathit{o}\mathit{v}\mathit{e}\mathit{r}\mathit{y}<Clandfill+Ccoke$$

(5)

$$\mathit{C}\mathit{r}\mathit{e}\mathit{c}\mathit{o}\mathit{v}\mathit{e}\mathit{r}\mathit{y}:=Qmpc\times Dmpc\times UCTmpc+Qcem\times Dcem\times UCTcem+Qcem\times Cgriding$$

(6)

$$\mathit{C}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}:=Qlandfill\times Dlandfill\times UCTlandfill+Qlandfill\times Cdispose$$

(7)

$$\mathit{C}\mathit{c}\mathit{o}\mathit{k}\mathit{e}:={\sum }_{i=1}^n\left({Qcoke}_i\times {Dcoke}_i\times {UCTcoke}_i\right)+Qcoke\times Vfmcoke+Qcoke\times Cacoke$$

(8)

where the following definitions hold:

$\mathit{C}\mathit{r}\mathit{e}\mathit{c}\mathit{o}\mathit{v}\mathit{e}\mathit{r}\mathit{y}$ represents the cost of energy recovery from decommissioned wind blades (USD);

$\mathit{Q}\mathit{m}\mathit{p}\mathit{c}\times \mathit{D}\mathit{m}\mathit{p}\mathit{c}\times \mathit{U}\mathit{C}\mathit{T}\mathit{m}\mathit{p}\mathit{c}+\mathit{Q}\mathit{c}\mathit{e}\mathit{m}\times \mathit{D}\mathit{c}\mathit{e}\mathit{m}\times \mathit{U}\mathit{C}\mathit{T}\mathit{c}\mathit{e}\mathit{m}$ represents the cost of transporting decommissioned wind turbine blades by road for energy recovery in a cement plant (USD);

$\mathit{Q}\mathit{c}\mathit{e}\mathit{m}\times \mathit{C}\mathit{g}\mathit{r}\mathit{i}\mathit{d}\mathit{i}\mathit{n}\mathit{g}$ represents the cost of crushing decommissioned wind turbine blades at the MPC (USD).

$\mathit{C}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}$ represents the cost of landfilling decommissioned wind blades (USD);

$\mathit{Q}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}\times \mathit{D}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}\times \mathit{U}\mathit{C}\mathit{T}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}$ represents the cost of transporting the wind turbine blades by road to the industrial landfill site (USD);

$\mathit{Q}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}\times \mathit{C}\mathit{d}\mathit{i}\mathit{s}\mathit{p}\mathit{o}\mathit{s}\mathit{e}$ represents the cost of disposing of decommissioned wind turbine blades in industrial landfill sites (USD).

$\mathit{C}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$ represents the cost of using petroleum coke in a cement plant (USD);

${\sum }_{\mathit{i}=1}^{\mathit{n}}\left({\mathit{Q}\mathit{c}\mathit{o}\mathit{k}\mathit{e}}_{\mathit{i}}\times {\mathit{D}\mathit{c}\mathit{o}\mathit{k}\mathit{e}}_{\mathit{i}}\times {\mathit{U}\mathit{C}\mathit{T}\mathit{c}\mathit{o}\mathit{k}\mathit{e}}_{\mathit{i}}\right)$ represents the sum of the cost of transporting petroleum coke by road from the refinery to the port and to the cement plant ($\mathrm{U}\mathrm{S}\mathrm{D}$);

$\mathit{Q}\mathit{c}\mathit{o}\mathit{k}\mathit{e}\times \mathit{V}\mathit{f}\mathit{m}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$ represents the cost of maritime transportation of petroleum coke from one port to another ($\mathrm{U}\mathrm{S}\mathrm{D}$);

$\mathit{Q}\mathit{c}\mathit{o}\mathit{k}\mathit{e}\times$ $\mathit{C}\mathit{a}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$ represents the acquisition cost of petroleum coke (USD).

For road transport, the unit cost of transporting one kilometer per tonne was estimated in Equation (9) below:

$$UCT≔{\displaystyle \frac{(Vfi+Vfv)}{p}}$$

(9)

where $UCT$ represents the unit cost of transport (USD/t.km), $(Vfo+Vfb)$ represents the value of freight per kilometer (round trip), which considers the minimum freight value [38] and inflation of 5.29% in 2022, and $p$ represents the payload to be transported. The dimensions and weights of the vehicles used for transportation were defined in accordance with Resolution 882/2021 of the National Traffic Council. In this study, monetary data was converted to US dollars (USD) based on the Central Bank of Brazil rate on 5 May 2023, when BRL 1 (Brazilian real) was equivalent to USD 0.20 (US dollar).

2.6. Evaluated Scenarios

The decommissioning of 1 tonne of wind turbine blades in the Northeast region of Brazil with the implementation of a centralized MPC was considered. Here, two decommissioning logistics scenarios were considered (Figure 2).

Base scenario: the decommissioned wind turbine blades are sent to industrial landfill sites licensed to dispose of class II waste and the petroleum coke (6.5% sulfur mass) is used as fuel in cement kilns.

Proposed scenario: the decommissioned wind turbine blades are transported to the MPC and, after segregation, crushing and mixing with solid recovered fuel (SRF), the crushed material is sent for energy recovery in cement kilns. This is a multifunctional scenario, which serves for material disposal and energy supply.

The material mix composed of fiberglass fabric, epoxy resin, polyurethane foam, protective coating, and adhesive on a mass basis was considered as material to be crushed for energy recovery in this study [30]. It represents 96.3% of the wind turbine blade mass. The balsa wood (2.3% w/w) can be reused to make furniture and pallets, and the metal material (1.4% w/w) can be melted down and converted into new products, which were not considered in this study. In addition, a loss of 5% of the mass of the wind turbine blade related to the processing of the wind turbine blade in the MPC was considered [39,40]. The material losses in the transportation of wind turbine blades were disregarded in this study.

For the base scenario, the average distance from wind farms to licensed industrial landfill sites was considered and that the petroleum coke (6.5% sulfur mass) used in the cement plants is produced by Philips 66 Company at Sweeny Refinery—TX and transported by truck to the Port of Houston—TX. It is then transported by ship to the Port of Aracajú—SE, as it is the port with the largest share of petroleum coke imports for cement production in the Northeast, and by truck to the cement plants, considering the average distances [41,42,43].

$Vfolandfill$ represents the value of the outward freight to the wind farm (empty truck) and $Vfblandfill$ represents the value of the return freight to the industrial landfill site (loaded truck), which was estimated at 0.95 USD/km and 1.04 USD/km, respectively. This considers the minimum freight value for general cargo and six-axle vehicles for hiring only motor vehicles (outward) of 0.90 USD/km and road freight transportation (return) of 0.99 USD/km [38] and inflation of 5.29% in 2022. The payload per truck is 10.32 tonnes (considering that each megawatt uses 10.32 tonnes of material). Thus, $UCTlandfill=$ 0.19 (USD/t.km).

The petroleum coke density for this study is 1040 kg/m³ [1] and the use of dump trucks with a volumetric capacity of 12.2 m³ because of the characteristic of the petroleum coke (Standard Dump Truck 16 yard³) [44]. For transportation from the Sweeny Refinery to the Port of Houston, the loaded dump truck carries 12.7 tonnes of petroleum coke per trip. In this case, the freights of the round trip are represented by $Vfocoke$ (loaded truck) and $Vfbcoke$ (empty truck). In the United States, the use of a truck is charged by the hour. The hourly cost is USD 130 (empty or loaded) [44], with the allocation of two hours for the loading and one-way trip plus two hours for the unloading and return trip. Thus, the coke transportation cost (round trip) is USD 520 from the Sweeny Refinery to the Port of Houston, which was used for $Vfocoke$ = $Vfbcoke$ = 2.48 USD/km. $UCTcoke$ for transportation in the United States is 0.39 (USD/t.km).

The maritime freight ($Vfmcoke$) for petroleum coke transportation from the Port of Houston to the Port of Aracajú is 22.96 USD/t [12]. For transportation from the Port of Aracajú to the cement plant, the use of six-axle bulk dump trucks with a volumetric capacity of 40 m³ was considered [45]. The freight rate per kilometer traveled for a six-axle dump truck is $Vfocoke$ 1.04 USD/km and $Vfbcoke$ 0.95 USD/km [38]. $UCTcoke$ for transportation in Brazil is 0.05 (USD/t.km). The main model input parameters of the base scenario are shown in

Table 1. Model input parameters for the transportation and disposal of 1 tonne of decommissioned wind turbine blades from the wind farm to the industrial landfill site and the acquisition and transportation of petroleum coke from the refinery to the cement factory in the base scenario.

Parameter	Transportation	Place of Origin	Place of Destination	$\mathit{Q}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}$(t)	$\mathit{D}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}$(km)	$\mathit{U}\mathit{C}\mathit{T}\mathit{l}\mathit{a}\mathit{n}\mathit{d}\mathit{f}\mathit{i}\mathit{l}\mathit{l}$ (USD/t.km)	$\mathit{C}\mathit{d}\mathit{i}\mathit{s}\mathit{p}\mathit{o}\mathit{s}\mathit{e}$  (USD/t)
Wind blade	Truck	Wind farm	Industrial landfill site	1	388	0.19	60
Parameter	Transportation	Place of Origin	Place of Destination	$Q\mathit{c}\mathit{o}\mathit{k}\mathit{e}$(t)	$\mathit{D}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$(km)	$\mathit{U}\mathit{C}\mathit{T}\mathit{c}\mathit{o}\mathit{q}\mathit{u}\mathit{e}$ (USD/t.km)	$\mathit{V}\mathit{f}\mathit{m}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$  (USD/t)	$\mathit{C}\mathit{a}\mathit{c}\mathit{o}\mathit{k}\mathit{e}$ (USD/t)
Petroleum coke	Truck	Sweeny refinery	Houston port	0.6	105	0.39	-	128.5
	Ship	Houston port	Aracajú port	0.6	-	-	22.96	-
	Truck	Aracajú port	Cement plant	0.6	930	0.05	-	-

$Qlandfill$: decommissioned blades; $Dlandfill:$ distance traveled from wind farm to industrial landfill site; $UCTlandfill$ unit cost of transport from the wind farm to industrial landfill site; $Cdispose:$ unitary cost for disposing of decommissioned blades. $Qcoke$: petroleum coke; $Dcoke$: distance traveled; $Qcoke$: unit cost of transport from the petroleum coke; $Vfmcoke$: one-way maritime freight from the Port of Houston to the Port of Aracajú; $Cacoke:$ acquisition cost of petroleum coke. The costs of landfilling 1 tonne of decommissioned wind blades and using petroleum coke in a cement plant were estimated from Equations (7) and (8), respectively.

.

For the proposed scenario, it was considered that 1000 kg of wind turbine blade material can replace 600 kg of fossil fuel [40], which was represented by petroleum coke, and that the decommissioned and cut up wind turbine blades are transported by truck from the wind farm to the MPC. When they arrive at the MPC, the metal material and balsa wood are separated, and the remaining material is crushed into pieces <40 mm in size. The crushed material is incorporated into SRF—an alternative fuel made from mixed dry recyclables that are too difficult to separate and would otherwise go to landfill—in the mass proportion of 50% crushed material and 50% SRF [27] and transported by truck to the cement plant for co-processing in the cement kiln. It was considered that the SRF and crushed material mixture received no further processing after crushing [27,46]. Even though the crushed material was mixed with SRF before using the fuel mixture in the cement kiln, only the energy content of GRP was considered in this study.

For the proposed scenario, $Vfompc$ represents the freight cost per kilometer to the wind farm (empty truck) and $Vfmpc$ represents the freight cost per kilometer back to the MPC (loaded truck) per kilometer, which was estimated at 0.95 USD/km and 1.04 USD/km and a payload of 10.32 tonnes, respectively, and $UCTmpc=0.19(\mathrm{U}\mathrm{S}\mathrm{D}/\mathrm{t}.\mathrm{k}\mathrm{m})$. It was assumed that the transportation was carried out by MPC’s own fleet. The SRF and crushed material mixture was transported to the cement plant using six-axle bulk dump trucks with a volumetric capacity of 40 m³ [45] that transports 10.8 t per trip in the loaded dump trucks, considering the SRF and crushed material mixture density of 270 kg/m³ [47]. In this case, $Vfocem$ represents the one-way freight for the loaded truck with 10.8 t and $Vfbcem$ represents the freight for the empty truck in the return trip. The freight rate for general cargo trucks is 1.04 USD/km in $Vfocem$ and 0.95 USD/km in $Vfbcem$ [38] and $UCTcem$ 0.18 (USD/t.km). The main model input parameters of the proposed scenario with a centralized MPC is shown in

Table 2. Model input parameters for the transport of 1 tonne of decommissioned wind turbine blade from the wind farm to the centralized materials processing center (MCP) and the material mixed into the solid recovered fuel (SRF) for energy recovery in a cement plant.

Parameter	Transportation	Place of Origin	Place of Destination	$\mathit{Q}\mathit{m}\mathit{p}\mathit{c}$(t)	$\mathit{D}\mathit{m}\mathit{p}\mathit{c}$(km)	$\mathit{U}\mathit{C}\mathit{T}\mathit{m}\mathit{p}\mathit{c}$ (USD/t.km)	$\mathit{C}\mathit{g}\mathit{r}\mathit{i}\mathit{d}\mathit{i}\mathit{n}\mathit{g}$(USD/t)
Wind blade	Truck	Wind Farm	MPC	1	608	0.19	127
Parameter	Transportation	Place of Origin	Place of Destination	$\mathit{Q}\mathit{c}\mathit{e}\mathit{m}$(t)	$\mathit{D}\mathit{c}\mathit{e}\mathit{m}$(km)	$\mathit{U}\mathit{C}\mathit{T}\mathit{c}\mathit{e}\mathit{m}$ (USD/t.km)
Crushed material in the SRF	Truck	MPC	Cement plant	0.92	454	0.18

$Qmpc$: decommissioned material; Dmpc: distance traveled from the wind farm to MPC; $UCTmpc:$unit cost of transport from the wind farm to MPC; $Qcem$: crushed material; $Dcem$: distance traveled from the MPC to the cement plant; $Cgriding$: cost for crushing decommissioned wind turbine blade; $UCTcem:$ unit cost of transport from the MPC to the cement plant. The cost of energy recovery from decommissioned wind blades was estimated from Equation (6).

.

An additional assessment was carried out based on five proposed decentralized MPCs in the Northeast region of the country for a comparison of the economic viability with the proposed scenario using a centralized MPC and the base scenario. The CG method was also used to define four additional MPCs in different states to complement the centralized MPC (described in item 2.4): Rio Grande do Norte (MPC-RN), Bahia (MPC-BA), Ceará (MPC-CE), and Paraíba (MPC-PB). To optimize the distances, the centralized MPC was included to receive waste from decommissioned wind blades from Maranhão, Piauí, and Sergipe, MPC-RN from Rio Grande do Norte, MPC-BA from Bahia, MPC-CE from Ceará, and MPC-PB from Paraíba and Pernambuco. An MPC installation in Piauí and Pernambuco was not considered due to the lack of cement plants licensed for co-processing in these states. Although Sergipe has two cement plants suitable for co-processing, there is only one wind farm in operation, so no MPC was considered in this state.

A sensitivity analysis was carried out considering the minimum, average, and maximum historical price of petroleum coke over the last 5 years. The minimum FOB (free on board) price was 27.50 USD/tonne in November 2019, the average price was 88.50 USD/tonne, and the maximum price was 128.50 USD/tonne in January 2023 [12].

3. Results

3.1. MPC Location

The wind power capacity in operation according to state in the Northeast of Brazil is shown in

Table 3. Number of wind farms, installed capacity, and waste material generation per state in the Northeast region of Brazil.

State	Territorial Area (km2) a	Number of Wind Farms b	Installed Capacity (MW) b	Accumulation of Wind Turbine Blade Waste in 20 Years—From 2023 to 2042 (t)	Concentration of Wind Turbine Blade Waste in 20 Years—From 2023 to 2042 (t/km2)
Bahia	564,760	247 (33%)	6433 (30%)	66,389	0.12
Rio Grande do Norte	52,810	223 (29%)	6747 (32%)	69,629	1.32
Piauí	251,755	104 (14%)	3379 (16%)	34,871	0.14
Ceará	148,894	100 (13%)	2516 (12%)	25,965	0.17
Pernambuco	98,068	39 (5.1%)	992 (4.7%)	10,237	0.10
Paraíba	56,467	30 (3.9%)	628 (3.0%)	6481	0.11
Maranhão	329,651	16 (2.1%)	426 (2.0%)	4396	0.01
Sergipe	21,938	1 (0.2%)	34 (0.1%)	351	0.02
Alagoas	27,831	-	-	-	-
TOTAL	1,552,174	760 (100%)	21,155 (100%)	218,319	0.14

^a IBGE [48], base year 2022; ^b ANEEL [28], data for 1 November 2022.

. The states of Bahia, Rio Grande do Norte, Piauí, and Ceará hold 89% of the wind power capacity in operation.

There were 760 wind farms in operation in the Northeast region, totaling an installed onshore capacity of 21,155 MW in 2022 [28]. The annual and cumulative estimates of the residual mass of wind turbine blades in the Northeast region, considering a useful life of 20 years for wind farms, are shown in Figure 3 [7,8].

The location coordinates of the centralized MPC defined in the CG method ($x$ = −7.626194003 and $y$ = −39.24288214), which was based on the coordinates of the wind farms and the projected residual blade mass to be generated in 20 years, are in the municipality of Jardim in Ceará, 450 km from Fortaleza, and 80 km from Juazeiro do Norte. Figure 4a shows the location of the wind farms. Figure 4b shows the location of the MPCs, industrial landfill sites, and cement plants with environmental licenses for co-processing in the Northeast.

3.2. Economic Viability Assessment

3.2.1. Base Scenario

The transportation cost to send 1 tonne of decommissioned blades from the wind farm to the industrial landfill site is USD 73.72. Considering that the cost per tonne of disposing of decommissioned wind turbine blades in industrial landfill sites ($Cdispose$) is USD 60/t [7,49], the waste management cost (transportation and landfilling) for the base scenario is USD 133.72.

The road and maritime transportation cost for delivering petroleum coke from the refinery to the cement plant is USD 66.25. This was estimated from the petroleum coke quantity, number of truck trips, the distance traveled, and the unitary transportation cost of road and maritime transport. The acquisition cost of petroleum coke is USD 77.10, considering that the unitary acquisition cost of petroleum coke ($Cacoke$) produced in the Gulf of Mexico—United States has a free on board (FOB) price of 128.5 USD/t [12]. Thus, the petroleum coke supply cost (transportation and acquisition) is USD 143.35. The total logistics cost (waste management and petroleum coke supply) for the Base Scenario is USD 277.07 (Figure 5).

3.2.2. Proposed Scenario—Energy Recovery with a Centralized MPC

The transportation cost for sending the decommissioned material from the wind farm to the centralized MPC is USD 115.52 and after this to the cement plant is USD 75.18, totaling USD 190.70. The first transportation part was based on the quantity of decommissioned material, the number of truck trips, the distance traveled from the wind farm to the centralized MPC and the unitary transportation cost. The second transportation part was based on the quantity of crushed material, number of truck trips, the distance traveled from the centralized MPC to the cement plant, and the unitary transportation cost. The processing cost for 1 tonne of decommissioned wind turbine blade is USD 127 [49]. Thus, the total logistics cost (transportation and processing of materials) for the proposed scenario is USD 317.70 (Figure 5).

3.2.3. Proposed Scenario—Energy Recovery with Decentralized MPCs

The transportation cost for the proposed scenario with a centralized MPC was higher than that of the base scenario. In this regard, decentralized MPCs were proposed to reduce transportation costs. The location of decentralized MPCs, cement plants, and industrial landfill sites licensed to dispose of class II waste in the Northeast are shown in Figure 4b.

The total cost of the scenarios evaluated for 1 tonne of decommissioned wind farm blade to be processed in a centralized MPC and in decentralized MPCs is shown in Figure 5, where the average distance from the wind farm to the decentralized MPCs is 233 km and from the decentralized MPCs to the cement plant is 266 km.

The total logistics cost for 1 tonne of decommissioned wind turbine blade from the wind farm in the proposed scenario with decentralized MCPs was USD 215.32, which is 22% lower than that of the base scenario, making it an attractive energy recovery option.

3.2.4. Logistics of the Decommissioned Wind Turbine Blades in the Brazilian Northeast

The quantity of decommissioned wind turbine blades was classified according to the economic performances for the base and proposed scenarios combined, considering the centralized MPC and the four additional decentralized MPCs (

Table 4. Decommissioned wind turbine blade destination in the Northeast region of Brazil based on the logistics cost for the base and proposed scenarios combined with the centralized and decentralized material processing centers (MPCs).

State	Decommissioned Wind Turbine Blades (t)	Base and Proposed Scenarios Combined—Centralized MPC				Base and Proposed Scenarios Combined—Decentralized MPCs
		Base Scenario (t)	Logistics Cost—Base Scenario (USD)	Proposed Scenario— Centralized MPC (t) a	Logistics Cost—Proposed Scenario (USD)	Base Scenario (t)	Logistics Cost—Base Scenario (USD)	Proposed Scenario— Decentralized MPC (t) b	Logistics Cost—Proposed Scenario (USD)
Bahia	66,389	57,340 (86%)	1.69 × 107	9049 (14%)	2.52 × 106	512 (1%)	1.19 × 105	65,877 (99%)	1.48 × 107
Rio Grande do Norte	69,629	69,629 (100%)	1.58 × 107	-	-	-	-	69,629 (100%)	1.22 × 107
Piauí	34,871	1711 (5%)	3.63 × 105	33,160 (95%)	8.83 × 106	1711 (5%)	3.63 × 105	33,160 (95%)	8.83 × 106
Ceará	25,965	20,007 (77%)	5.28 × 106	5958 (23%)	1.76 × 106	-	-	25,965 (100%)	4.64 × 106
Pernambuco	10,237	6011 (59%)	1.53 × 106	4226 (41%)	1.06 × 106	1161 (11%)	2.78 × 105	9076 (89%)	2.30 × 106
Paraíba	6481	6481 (100%)	1.53 × 106	-	-	-	-	6481 (100%)	1.23 × 106
Maranhão	4396	4396 (100%)	1.63 × 106	-	-	4396 (100%)	1.09 × 106	-	-
Sergipe	351	351 (100%)	7.77 × 104	-	-	351 (100%)	9.41 × 104	-	-
Total	218,319	165,926 (76%)	4.31 × 107	52,393 (24%)	1.42 × 107	8131 (4%)	1.94 × 106	210,188 (96%)	4.40 × 107

Base scenario: Industrial landfill site and petroleum coke supply; Proposed scenario: Energy recovery. Total crushed material produced: 48 202t ^a; 193 373t ^b.

). The logistic cost for the base and proposed scenarios combined with one centralized MPC was USD 5.73 × 10⁷, which was reduced by 20% in the base and proposed scenarios combined with decentralized MPCs (USD 4.59 × 10⁷). The decentralized MPCs enable the economic viability of the crushed material energy recovery to increase from 24% to 96% compared to the centralized MPC (Table 4). For Bahia, the portion of energy recovery for crushed material from wind turbine blades increased from 14% to 99%, in Rio Grande do Norte from 0 to 100%, in Ceará from 23% to 100%, in Paraíba from 0 to 100% and in Pernambuco from 41% to 89% in a mass basis with decentralized MPCs. Meanwhile, for the states of Piauí, Maranhão, and Sergipe there was no difference as the centralized MPC is nearer to the wind farms than the decentralized options.

Regarding the use of decentralized MPCs, MPC-RN is expected to process the greatest mass of decommissioned wind turbine blades (33%), followed by MPC-BA (31%), MPC centralized (16%), MPC-CE (12%), and MPC-PB (7%) (Figure 6).

3.2.5. Sensitivity Analysis—Fluctuations in Fuel Prices

The sensitivity analysis (Figure 7) shows that, considering the five years petroleum price, a proposed scenario with decentralized MPCs presents a lower cost (USD 215.32) than that for the base scenario with minimum (USD 216.47), average (USD 253.07), and maximum cost (USD 277.07). However, the price of petroleum coke below the minimum presented for the last five years may make it impossible for the energy recovery from decommissioned blades in cement kiln.

4. Discussion

The abandoning of wind farms before operation or after the end of their useful life, without proper decommissioning, puts the surrounding population at risk. These wind farms end up becoming an open dump for solid waste and the accumulation of standing water, a source of accidents caused by falling parts, and an undesirable visual appearance. For instance, the Fernando de Noronha 1 wind turbine with an installed capacity of 75 kW (which began operation in 1992) and Fernando de Noronha 2 with an installed capacity of 225 kW (operation started in 2001) have been decommissioned [50]. However, the Morro do Camelinho wind farm with an installed capacity of 1000 kW has been deactivated since 2015 and the turbines remain assembled and exposed to the weather [51]. The construction of the Casa Nova I Wind Farm with a planned installed capacity of 180 MW was stopped in 2014 due to the company bankruptcy. Of the 120 wind turbines contracted, only 30 were assembled, but these were abandoned before operation [52]. However, this project was expected to be reactivated in 2023 by a new company [53].

Rio Grande do Norte has the highest concentration of the projected wind turbine blade waste accumulation in 20 years (1.32 t/km²), namely nine times that of the average concentration for the Brazilian Northeast (0.14 t/km²) and eight times higher than the second place—Ceará (0.17 t/km²) (Table 3). These results indicate that public policies for the environmentally appropriate management of wind turbine blade material should be prioritized in Rio Grande do Norte. This is due to the highest concentration of open dumps being in the Northeast region of Brazil, totaling 899 units, along with 108 sub-controlled landfills [54]. Both are considered unsuitable options for the final disposal of solid waste classified as rejects due to soil and groundwater contamination by leachate, disease spread, greenhouse gas emission, and burning risk. The quantity of sanitary landfill sites in the Northeast region is 69, which represents only 10% of the total in Brazil [54]. In this context, the distribution of the urban solid waste disposed of in the Northeast region was 9.98 million tonnes in sanitary landfills (53.3%), 5.83 million tonnes in open dumps (31.1%), and 2.91 million tonnes in sub-controlled landfills (15.6%) in 2021 [54].

The National Solid Waste Policy stipulated in article 54 that municipalities should implement the proper final disposal of waste by 2014 [55], but the deadline has not yet been met. According to the New Sanitation Framework approved in July 2020, open dumps and sub-controlled landfills in Brazil are expected to be phased out by 2024 [56]. Even though wind turbine blades are classified as non-hazardous solid waste [57], human contact with exposed fiberglass after inadequate disposal can lead to irritation of the skin (dermatitis), eyes, and internal organs if ingested [58]. Therefore, it is timely to implement norms for prohibiting inadequate wind turbine blade disposal. On this basis, the Brazilian government published the National Circular Economy Strategy under Federal Decree No. 12.082/2024 with the aim of promoting the transition from the linear production model to a circular economy, thus encouraging the efficient use of natural resources and sustainable practices throughout the production chain [59]. In addition to other sustainable finance instruments, the Tax Reform initiated in 2023 also makes significant contributions to ecological transformation in Brazil. The National Regional Development Fund was created with the aim of reducing regional and social inequalities, with resources that should prioritize projects and actions for environmental sustainability and the reduction in greenhouse gas emissions. The Tax Reform also provides “Selective Tax” incentives for the purchase of waste and other materials destined for the recycling, reuse, or reverse logistics from individuals, cooperatives or other forms of grassroots organization [60]. Those incentives could be beneficial for the energy recovery of decommissioned wind blades in cement kilns in Brazil.

After concerns about 25,000–50,000 tonnes of blades being annually disposed of in European countries, The European Wind Energy Association called for a ban on sending decommissioned wind turbine blades to landfill sites waste by 2025 to accelerate the development of more sustainable technologies [61]. On the other hand, the American Wind Energy Association proposes the disposal of wind turbine blades in industrial landfill sites for the 70,000–134,000 tonnes annually projected between 2020 and 2050, as this is considered a low volume of waste material when compared to urban waste that is sent to landfills [62]. Regarding the Brazilian region of the Northeast, the estimated waste material generation from decommissioned wind turbine blades is 22,600 tonnes annually on average between 2034 and 2042 (Figure 3), while municipal solid waste mass disposed of in sanitary landfills in the Northeast region was 9,980,000 tonnes in 2021 [54]. Therefore, waste material from decommissioned wind turbine blades represents 0.2% of the total urban waste mass landfilled in the Northeast region.

Recycling GRP has the advantages of reducing the extraction of natural resources, minimizing the carbon footprint compared to more energy-intensive materials and the reduced generation of waste materials for final disposal [63]. The challenge of recycling GRP from wind turbine blades is to transform it into a product with equal or greater added value than the original fiberglass and polymer resin. Some companies collect GRP waste, such as the wind energy, aerospace, and maritime sectors, and manufactures plastic tubing, pallets, panels for the exterior of buildings, soundproofing panels, construction sites, traffic, and other noisy activities create durable and smart urban furniture [63,64,65]. However, recycling has technical and economic limitations that make it less competitive to replace virgin raw materials on a large scale in the short term: mechanical recycling shows the degradation of the fiber’s mechanical properties and only short fibers are recovered, pyrolysis is not yet economically viable and requires high energy consumption, and fluidized bed and solvolysis are still in the laboratory evaluation phase. The challenges of both physical and chemical recycling technologies are that the more aggressive loading, necessary for cleaner material separation and preventing residues on recovered fibers, can lead to damaging the fibers, reducing their value and usability options, and making the recycling process less environmentally friendly [21,66].

Of the ready-to-go recycling options (TRL 9), mechanical recycling is the only one to create profit. The cost of mechanical recycling is very low compared to other recycling processes as this process is less complex and shows a profit of USD 284 per tonne [67]. For pyrolysis, a thermal process, the energy consumption is high, and more equipment is necessary. The yield and performance of the fibrous product recovered by the thermal processes are also lower than those of mechanical recycling. Hence, recycling GRP blade waste using pyrolysis is unlikely to be profitable, with projected additional costs standing at over USD 140 per tonne. Research and development investments are required to increase process efficiency and reduce energy consumption to further reduce the recycling cost [67].

Solid waste co-processing in cement kilns has been practiced for more than 20 years in Brazil. Co-processing is regulated at the federal level by CONAMA 499/2020 [68] and some states have complementary legislation. Three million tonnes of waste materials from various sources were co-processed in 2022, 94% of which were biomass fuel and alternative fuels, and 6% were alternative raw materials (contaminated soils, casting sand, iron ore substitutes, among others) [69]. A total of 25.8 million tonnes of materials were co-processed in cement kilns between 1999 and 2022, which were no longer disposed of in landfill sites and replaced fuels used by the cement industry [69]. Solid waste co-processing in cement kilns is a short-term option that contributes to the eradication of open dumps, while increasing the useful life of landfills, improving public health, preserving natural resources, reducing greenhouse gas emissions, and lowering thermal energy costs [69] as the cement production emits large amounts of carbon dioxide and has long been considered a significant source of global atmospheric CO₂ emissions [24].

The decommissioned wind turbine blade data indicate that, assuming the operation start of the MPC in 2023, the material processing quantity in the first 10 years is 7% of the total projected for 20 years (Figure 3). Therefore, it is more attractive to implement a smaller MPC during this initial period and then install additional decentralized MPC units. There are two wind turbine blade manufacturing facilities in the Northeast region, one in Ceará [70] and the other in Pernambuco [71]. Regarding manufacturing waste, both companies send the GRP waste to local landfills where non-hazardous industrial solid waste is disposed [72]. The manufacturer Wobben Windpower, which provided different models of wind blades that are in operation in Brazil, closed its activities in Sorocaba, state of São Paulo, in 2019 [73] and in Ceará in 2020 [74]. This could limit the repowering or extension of the useful life of those blades in the country because it is costly to manufacture a custom wind turbine blade abroad due to the time it takes to import it, the financial costs (purchase, transportation, and customs duties), and the carbon footprint of the component.

Sultan, Mativenga, and Lou [31] used the CG method to identify the optimal location for an MPC, considering the GRP waste generated by each wind farm in the United Kingdom (UK) over three time periods: 2018, 2030, and 2048. However, the authors did not assess the economic viability of the decommissioned wind turbine blade logistics. The UK has an area of 241,930 km² [75], while the Northeast region of Brazil has an area of 1,552,174 km² (Table 3). This study showed that the total cost for the energy recovery of 1 tonne of decommissioned wind turbine blades, considering the location of the centralized MPC which was defined by the CG method, was 317.70 USD/t (Figure 5). This was higher than the cost for the base scenario (sending to an industrial landfill site and using petroleum coke imported from the Gulf of Mexico—TX in the cement plant) which was 277.07 USD/t (Figure 5). Next, it was found that the installation of decentralized MPCs makes it economically viable to recover energy from the wind turbine blades of wind farms as the total cost was 215.32 USD/t (Figure 5). This shows that decentralized MPCs are more appropriate for the Northeast region of Brazil to make energy recovery from wind turbine blades viable in the region (Figure 4b).

Despite its higher initial cost, the implementation of decentralized MPCs can benefit from the treatment of waste from the manufacturing stage of the two factories installed in the Northeast that produce wind turbine blades not only for the national market but also for exportation, as 10% loss of material impregnated with fiberglass and epoxy resin is sent to landfill and could be sent to energy recovery [72]. Moreover, offshore wind parks, which do not yet exist in Brazil, are in the environmental licensing phase with the competent national regulator [76] and will require the manufacturing of larger wind turbine blades and, consequently, environmentally appropriate disposal at the post-use stages.

The cost of transportation is the main factor that defines the economic viability of the energy recovery from decommissioned wind turbine blades in Northeast Brazil (Figure 5). In addition, the substitution factor for crushed material from wind turbine blades and petroleum coke is 5:3 (1000 kg of crushed material can replace 600 kg of fossil fuel [40]) and the petroleum coke density is 1040 kg/m³ [1] compared to that of crushed material which is 270 kg/m³ [47]. Therefore, higher truck transportation costs are required for the decommissioned wind turbine blades compared to the petroleum coke (Figure 5).

The GRPs are also used in other industries beyond the wind industry because of the following advantages: low weight, high resistance to wear and corrosion, and mechanical characteristics which allow the reduction in energy consumption in automotive, aeronautic, and naval applications [77]. Furthermore, the GRPs are used in building and infrastructure to obtain structures with higher resistance to support heavy loads and electric and electronics applications. The expansion of the use of the MPCs, considered for the wind industry waste in this study, has the potential to increase the MPC use and reduce the installation downtime, extend the benefit of energy recovery from composite material waste compared to disposing in landfill for other industries, and reduce the dependence of importing petroleum coke from abroad to be used in cement plants in Brazil.

The petroleum coke used in Brazilian cement plants in 2020 comes from the USA (60%), characterized by a high mass sulfur content (6.5% w/w); Venezuela (10%), with a medium mass sulfur content (4.5% w/w to 5.5% w/w); and Brazil (30%), with a low mass sulfur content (less than 1% w/w), which is called green coke [78]. The instability in the price of petroleum coke, which has been on the rise in recent decades, and the high carbon footprint from its use have led industries to look for sustainable fuel alternatives [79]. The sensitivity analysis in Figure 7 shows that, when petroleum coke had the minimum, average, and maximum price, the cost for the base scenario was USD 216.47, USD 253.07, and USD 277.07, respectively. These values are higher than those of the proposed decentralized scenario (USD 215.32), demonstrating that the installation of decentralized MPCs is viable for replacing petroleum coke in cement kilns from the residue of decommissioned turbine blades. There are commercial installations in Europe for the energy recovery from decommissioned wind turbine blades and a successful pilot project has been built in the USA for GRP material from boats. However, there were no commercial facilities in the USA for the use of composites with energy recovery in 2020 [46], which is a promising route for the coming years. Moreover, the use of energy recovery from decommissioned wind turbine blades on a commercial scale has not been identified in Brazil.

Energy recovery in cement plants is economically viable for 95% of the decommissioned wind turbine blades in wind farms operating in the Northeast region of Brazil for the proposed scenario with decentralized MPCs (Table 4 and Figure 6), a promising route for the coming years. Furthermore, it can support the cement industry’s efforts to reduce the carbon footprint of its operations related to fossil fuel burning [69]. Decentralized MPC-RN and MPC-BA together can process 64% of the decommissioned wind turbine blades in the region (Figure 6). This means that public policies and planning should prioritize the construction and operation of MPCs in these states.

5. Conclusions

The lack of technical and economic feasibility studies on circular economy models hinders their dissemination to promote sustainable development. In this way, this study supports innovation in wind blade waste management with an emphasis on available at the highest technological readiness level (TRL 9) and economically viable solutions. Wind energy has expanded worldwide, and the first wind farms have reached the end of their useful life, which requires adequate solutions for the residual materials. The disposal of this material in the United States has been in industrial landfill sites, while in Europe, the option has been energy recovery. The co-processing of solid waste has been practiced by Brazilian cement plants for more than 20 years, which indicates that energy recovery from decommissioned wind turbine blades in Brazil is a promising technological route in the short term. This presents the following advantages: a nobler destination compared to industrial landfill sites, the potential for reducing the carbon footprint of cement plants, and the target achievement for increasing the use of alternative inputs in the cement industry’s energy mix, which can have economic benefits especially at times of rising fossil fuel prices. In this regard, the economic viability of the energy recovery logistics from decommissioned wind turbine blades sent to a centralized material processing center (MPC) and after to a cement kiln was evaluated in comparison to sending them to an industrial landfill site plus petroleum coke supply for the cement kiln in the Brazilian Northeast.

When evaluating the decommissioning of 1 tonne of wind turbine blade, the logistics cost of the base scenario (landfill of wind turbine blade and supply of petroleum coke to the cement plants) was lower than that of the proposed scenario (recovery of energy from the crushed wind turbine blades at the cement plants) with a centralized MPC located in Jardim—CE defined by the center of gravity (CG) method. The transport cost for the proposed scenario with a centralized MPC (USD 190.70) is higher than that of the base scenario (USD 139.97), because the average distance travelled from the wind farms to the centralized MPC ($Dmpc$) is 608 km, and the distance traveled from the centralized MPC to the cement plant ($Dcem$) is 454 km, while the average distance traveled from wind farms to industrial landfill sites $\left(Dlandfill\right)$ is 388 km. In this first case, the logistics for disposing of decommissioned wind blades in an industrial landfill site proved to be a lower-cost route compared to that of energy recovery.

The installation of decentralized MPCs by optimizing the distances and material quantities of wind turbine blades to be decommissioned in the 20 years horizon proved to be an economically viable option for 96% of the wind turbine blades in operation in the Northeast region of Brazil. The total logistics cost of the proposed scenario for energy recovery with decentralized MPCs was lower than that of the base scenario due to the reduction in transport costs as the average distance travelled from the wind farm to the decentralized MPCs ($Dmpc$) is 233 km and the average distance travelled from the decentralized MPCs to the cement plants ($Dcem$) is 266 km.

Energy recovery from decommissioned wind turbine blades in the Northeast region of Brazil is a promising route in the short term if transportation costs are optimized. In this regard, a centralized MPC is insufficient to meet the decommissioning of wind farms that are spread over 1,552,174 km², and therefore, MPC implementation should be prioritized in a decentralized manner. However, future studies are needed, such as life cycle assessment (LCA), to assess the energy and environmental performance of wind turbine blade decommissioning logistics for energy recovery in a cement kiln compared to industrial landfill site in the Brazilian Northeast to support sustainable decision making in the wind energy sector. Furthermore, studies need to be carried out on the other TRL technologies, as well as other sustainability metrics such as LCA.