**Mariusz Ta ´nczuk 1,\*, Robert Junga 1, Alicja Kolasa-Wi ˛ecek <sup>2</sup> and Patrycja Niemiec <sup>1</sup>**


Received: 2 January 2019; Accepted: 25 March 2019; Published: 1 April 2019

**Abstract:** Animal waste, including chicken manure, is a category of biomass considered for application in the energy industry. Poland is leading poultry producer in Europe, with a chicken population assessed at over 176 million animals. This paper aims to determine the theoretical and technical energy potential of chicken manure in Poland. The volume of chicken manure was assessed as 4.49 million tons per year considering three particular poultry rearing systems. The physicochemical properties of examined manure specimens indicate considerable conformity with the data reported in the literature. The results of proximate and ultimate analyses confirm a considerable effect of the rearing system on the energy parameters of the manure. The heating value of the chicken manure was calculated for the high moisture material in the condition as received from the farms. The value of annual theoretical energy potential in Poland was found to be equal to around 40.38 PJ. Annual technical potential of chicken biomass determined for four different energy conversion paths occurred significantly smaller then theoretical and has the value from 9.01 PJ to 27.3 PJ. The bigger energy degradation was found for heat and electricity production via anaerobic digestion path, while fluidized bed combustion occurred the most efficient scenario.

**Keywords:** biomass; chicken manure; proximate and ultimate analysis; energy potential

#### **1. Introduction**

In recent years, changes in the energy policies of all member states of the European Union (EU) have been aimed at increasing the proportion of renewable energy sources (RES) in the energy supply. As a consequence of these changes, legal regulations are being introduced to increase the share of RES in the total energy balance of the European community. The efforts made by the specific governments have, accordingly, focused on the application of the common and accessible RES such as solar, wind, water and biomass. In particular, biomass, is a very promising type of RES, which demonstrates considerable diversity in terms of physicochemical properties leading to wider potential applications in the energy industry [1]. The determination of the energy potential of various types of biomass, including bio-wastes, is indispensable for the development of technologies of biomass to energy conversion as well as for effective implementation of existing technological solutions.

Poultry manure (excreta) is a problematic biomass waste. Due to the increasing concentration of poultry in holdings, the issue of removal and utilization of the manure plays an important role. Soil conditioning—the manner in which this type of manure has been predominantly utilized up to this time—has a number of drawbacks [2], yet it has been the most popular one. This technique is applied all over the world but causes hazards to both crops and human health as a consequence of the negative effect of decomposing manure on various components of the natural environment. The effect of excessive soil conditioning can take the following forms: eutrophication, phytotoxic effects on succeeding crops, propagation of pathogens, pollution of atmospheric air and emission of

greenhouse gases [3]. In Poland, using chicken manure as a raw material in crop fertilization as well as in mushroom cultivation are two main ways of its application and utilization. According to [4] total volume of annually generated chicken manure in Poland is enough to fertilize over 20% of crops in environmentally balanced way in terms of nitrogen concertation. It should be underlined again that massive use of poultry manure as an organic fertilizer creates a strong risk of environmental degradation due to over-fertilization. Moreover, ammonia (NH3) atmospheric emissions from chicken manure land spreading can be several dozen times greater than emissions from combustion [5]. For this reasons it is necessary to define and apply new routes of poultry manure treatment in a sustainable way for the environment not only in Poland but in every location where these wastes are utilized mainly through soil conditioning.

One of the solutions to prevent negative environmental impact of chicken manure treatment is using it for energy generation. This can be of great interest to industry, unfortunately it is still rarely used in energy sector due to its unique chemical composition. There are several ways in which chicken manure can be used for generation of energy or for deriving improved fuel. It can be treated in such processes as fermentation (digestion), esterification, pyrolysis, gasification, co-gasification, combustion and co-combustion [3,5–7]. For more efficient energy generation it is necessary to pre-process or pre-treat chicken manure by physical and/or thermo-chemical processes such as drying, torrefaction, pyrolysis, steam treatment, and ozone treatment [6].

According to [8] chicken manure can be a promising substrate for slow pyrolysis, but the product of pyrolytic conversion should by bio-coal rather than syngas. The gasification of poultry-derived waste has been limited to laboratory and small-scale applications, whereas full and pilot scale installations operating in industrial conditions are incidentally mentioned in the literature. Experiments on gasification and co-gasification systems using both fixed and fluidized bed combustors show that to obtain a high quality fuel gas, the addition of another type of biomass or coal is desirable [9]. Combustion and co-combustion of poultry derived waste is the best known process of its thermal utilization: industrial scale installations are operated worldwide, including UK, USA, Netherlands, Ireland, Australia, Belgium, France, Germany, Italy, Spain [7], confirming the economic feasibility of the application. Despite the wide range of high-temperature thermal routes of chicken manure utilizations, in Poland only digestion processing is used so far. A raw chicken manure feedstock of 690 Mg/h supplies a biogas installation of 25–30 kW located directly on the farm in Pszczyna city. Incidental larger biogas units with capacity up to 1 MW are operated in the co-fermentation mode with mixing of waste from agricultural production and processing. The way of utilizing chicken manure as a kind of alternative fuel can be of interest in particular in the countries where hard coal still forms the basic source of energy and the number of poultry producers is relatively large. Local boilers situated in the vicinity of farms appear to be an area with great potential for application of this type of biomass. The heat produced in this manner can be used for heating local buildings [10]. Advanced technologies can also be applied for distributed electricity generation on chicken farms [5].

Poland meets two basic criteria that indicate the feasibility of utilizing chicken manure for energy. The first one is associated with the considerable chicken population on farms in Poland which is a leading poultry producer in Europe. According to European Egg Processors Association (EEPA) [11], Poland was listed in fourth place among all EU states in terms of laying hens population in 2016 (11.3 % of the EU-28), next to Germany (13.7%), France (12.6%), Spain (11.4%), United Kingdom (11.0%), Italy (10.8%) and Netherlands (8.9%). According to Food and Agriculture Organization of the United Nations (FAO) [12], in 2016 Poland was listed in second place among all EU states in terms live chickens (12.0% of the EU-28), next to Germany (13.0%), France (11.9%), United Kingdom (11.1%), Italy (10.1%), Spain (10.1%) and Netherlands (7.5%). The second one is associated with the dominant share of coal-fired sources in the production of heat: coal and coal products account for 86% of total heat production in Poland [13], similar to some other European countries where coal continues to dominate in the structure of the heat production system [14,15]. Additionally, Poland has the dominant share of coal-fired sources in the production of heat and electricity supplying chicken farms.

The latter part of this work aims to determine the quantitative and energy potential of chicken manure in Poland on the basis of the proposed methodology. Energy potential was assessed regarding two potential levels: theoretical and technical. As mentioned before, there are many technical ways for conversion chicken manure into useful forms of energy such as heat and electricity. The most common and widely used and technically advanced solutions were chosen as possible and representative conversion scenarios for the case of technical potential assessment analysis:

