**1. Introduction**

Energy self-sufficiency and low-carbon-economy transition are the concepts currently forcing the coal-based energy industry to significantly decrease its produced emissions. The annual consumption of coal (in coal-based industries) in the Czech Republic is over 60 million tons per year, ranking Czech Republic at 17th in worldwide consumption [1]. The Czech energy industry is also dependent on imports of 97% of oil and gas [1]. Several measures were adopted to reduce energy import dependence, including implementation of a higher share of renewable energy sources and more efficient use of

fossil fuels such as brown coal [1]. However, the transition process cannot be sudden and must be gradually implemented by viable investments. One such investment, which seems to be feasible for the current Czech energy industry but also usable for steel industries, is carbon capture technologies (CCTs). These technologies must be carefully assessed and planned for the specific conditions of a given country. There are three parameters that must be considered for the feasibility assessment of CCT—(i) technological feasibility, (ii) economic performance, and (iii) environmental performance. This paper considers each of these three parameters in a new combined analysis.

In the conditions of the Czech operational power units, several CCT options were considered, such as post-combustion technologies of ammonia scrubbing, activated carbon adsorption (PCC-A), and pre-combustion integrated gasification gas cycle with integrated carbonate loop (IGCC-CaL). These technologies are the subject of intensive research and optimization to achieve their implementation into the operational power units. The decision-making process for the choice of suitable technologies may be significantly influenced by environmental performance consideration via comprehensive methodology. Life cycle assessment (LCA) is one of the best certified methods to create environmental models of the considered systems. LCA allows the comparison of the assessed systems among each other [2].

The ammonia scrubbing process of LCA was already performed [3]. The ammonia scrubbing process increased the impact of fossils depletion and mineral resource depletion in comparison with the power unit (250 MWe) without CCT. That is caused by a large amount of additional energy consumption for ammonia solvent preparation. Moreover, energy efficiency of the power unit decreased from 38% to 27%. The environmental problem occurs with the treatment of ammonia salts, currently considered as non-utilized waste. On the other hand, CO2 was captured in a ratio of 90%.

An LCA for the PCC-A system for Czech conditions was recently published by the authors of this paper [4]. The LCA model in the study considers a functional unit nominal power output of 250 MWe. The paper concludes that adding such technology would increase the energy demand (an additional 1133 MJ for hard coal activation) and fossils depletion. The reason for this is the resource consumption of hard coal (additional fresh carbon 23 kg/h) in the production chain of the activated carbon.

IGCC-CaL was not previously assessed for the Czech conditions from the environmental point of view. However, several studies were made for the IGCC systems integration and its environmental assessment. A summary of the following studies can be found in Table 1.

The extensive study by Singh et al. [5] compares the environmental results for 400 MWe power plants with post, pre, and oxy-fuel combustion capture systems. For pre-combustion systems with IGCC based on Selexol absorption, the CO2 capture ratio is 90%, with an energy efficiency of 37.6%. Comparative LCA was made by hybrid LCA approach, using input–output analysis together with the ReCiPe 2008 version 1.02 method. Environmental results of a pre-combustion system show a reduction of 78% in the category of global warming potential (GWP), the highest reduction in comparison with the aforementioned systems. On the other hand, IGCC system contributes to increase of 120% in category of freshwater eutrophicaton (FE), influenced mainly by infrastructure development.

Cormos C. [6] evaluated the techno-economic and environmental performance of IGCC system for power plant concepts of a net power output of about 400–500 MWe. The study states that the introduction of the CCT system decreased net plan energy efficiency by 7.1–9.5%. The environmental part of the study compared the IGCC systems based on the physical solvent Selexol. Environmental impacts refer to the production of 1 kWh of electricity. However, the impacts were categorized in normalized mass and energy flows where the integration of the IGCC systems caused an increase of coal (25%), oxygen (24%), and cooling water (22%) consumption, and the ratio of captured CO2 was modelled at 90%.


*Energies* **2020**, *13*, 4188

**Table 1.** Review of references focused on

global warming potential (GWP),

environmental

acidification

 potential (AP), fossils depletion (FD),

 assessment of

pre-combustion

 integrated gasification

eutrophication

 potential (EP), terrestrial

 gas cycle technology with CO2 capture

acidification

 (TA), and freshwater

(IGCC-CCT),

In another study [7], three following three systems were compared: (i) a conventional supercritical coal power system, (ii) an IGCC-CCS system based on Selexol solvent system, (iii) and an IGCC without CCS. The systems were chosen according to equal coal consumption rather than equal electricity production. The environmental results for IGCC systems per 1 MWh are based on mass–energy balances and show higher water consumption due to the gasification process and the shift reaction in comparison to the power unit without CCT. The IGCC system with CO2 capture was designed for 81% CO2 capture ratio. The IGCC-CCS system reduced net energy efficiency from 32.1% (IGCC without CCS) to 26.1%.

The work of Petrescu et al. [8] compares IGCC power plant with gross electric output of 570.61 MWe and 2 IGCC-CCS systems. Two compared IGCC-CCS systems are based on Ca-based (IGCC-CaL) sorbents and iron-based oxygen carriers (IGCC-FeL). The used method for LCA analysis was CML 2001 using GaBi software. In both scenarios, the highest values refer to GWP, where the majority (85%) comes from coal mining and extraction. The results show that the highest carbon capture rate happens with IGCC-FeL (99.45%), with a net electrical efficiency drop from 45.09% to 38.76%. Energy efficiency dropped for IGCC-CaL from 45.09% to 36.44%, and the capture rate was 91.56%.

Regarding CaO looping, some studies were done for post-combustion CO2 capture. One study [9] considers 600 MWe supercritical pulverized coal power plant as a basis for CCT. According to the study [9], net energy efficiency drops from 39% to 32% due to CaO looping. LCA analysis was done at the endpoint level via SimaPro v8.3 software. The results indicate an increase in resources depletion, ozone depletion, and toxicities. The climate change impact was reduced by 72%.

Clarens et al. [10] compared a sub-critical coal power plant without CCT (500 MWe; net plant efficiency 36.9%), post-combustion capture technologies based on amine absorption (Econamine and Econamine FG+), and CaO looping without capture. This study used the LCA method of ReCiPe v1.04 and Simapro software. The CaO looping results in the best environmental performance among all systems in the categories of ozone depletion, photochemical ozone formation, particulate matter, and water depletion impacts. The CO2 capture ratio was 90% in each CCT systems. However, the net plant efficiency for the Econamine case dropped from 36.9% to 22.3%, for Econamine FG+ to 25.9%, and for CaO loop to 29.6%.

The literature survey clearly shows that very few environmental assessments were done on the subject of pre-combustion IGCC-CaL and none for comparison of IGCC-CaL and PCC-A. Moreover, the data in the studies is, in the majority, based on literature sources and heat-mass models rather than real case studies. Also, the selected environmental assessment methods were based on mass-energy flows analysis or methods such as hybrid LCA or CML.

The first part of the paper is focused on the environmental study that compares both CCT systems integrated into their reference power plants. The environmental study does not evaluate the reference power plants without CCT due to lack of data for a single IGCC system. Moreover, IGCC-CaL was designed as the one whole technology with an already integrated CCT system. Yet, in the case of PCC-A, a recent study [4] published by the same authors compares the reference 250 MWe power unit and the same reference power unit with PCC-A.

The second part of the paper is the economic study of both systems. The economic part compares the investments of both systems (IGCC-CaL, PCC-A) with the case of the energy system without CCT based on the cost and market trend of CO2 allowances.

The third part of the paper combines environmental and economic results to determinate the specifics that can influence the decision-making process for the final technology selection.

The paper has several contributions:


The paper is structured as follows: Section 2.1 defines the LCA methodology, Section 2.2 defines the economical assessment method, Section 3.1 provides a technical description of case study 1, Section 3.2 provides a technical description of case study 2, Section 3.3 defines the systems boundaries, Section 3.4 describes a life cycle inventory, Section 3.5 defines the cost effectiveness parameters, Section 4.1 presents the results of the life cycle impact assessment. Section 4.2 presents the Pareto analysis, Section 4.3 presents the results for cost effectiveness comparison, and Sections 5 and 6 provide the discussion and conclusions.
