An Analysis of the Energy Potential of Anaerobic Digestion of Agricultural By-Products and Organic Waste
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An Analysis of the Energy Potential of Anaerobic Digestion of Agricultural By-Products and Organic Waste S. Menardo & P. Balsari
Published online: 22 March 2012 # Springer Science+Business Media, LLC 2012
Abstract Anaerobic digestion is a promising option for recycling agricultural by-products and some organic wastes. While both agricultural by-products and wastes have no direct commercial value, their management is both complicated and costly. One option to simplify by-product management and reduce the costs associated with biogas plant feedstock is to substitute dedicated crops with vegetal by-products. Given that the chemical composition of some of these by-products can differ considerably from more typical biogas plant feedstock (such as maize silage), more complete knowledge of these alternatives to produce environmentally friendly energy is warranted. To this end, batch trials under mesophilic conditions were conducted to evaluate the potential biogas yield of many agricultural by-products: maize stalks, rice chaff, wheat straw, kiwi fruit, onions, and two expired organic waste products (dairy and dry bread) from the retail mass-market. Among the considered biomasses, the highest methane producer was the expired dairy product mixture, which yielded 554 lNCH4 kg−1 volatile solids (VS). Maize stalks and wheat straw produced the lowest yields of 214 and 285 lNCH4 kg−1VS, respectively. An assessment of the biogas and methane yields of each biomass was also undertaken to account for the specific chemical composition of each biomass as it can affect the anaerobic digestion operating system. Finally, the total Italian green energy production that might be derived from feeding all these biomasses to a biogas digester was estimated, in order to understand its potential impact. S. Menardo (*) : P. Balsari Department of Agriculture, Forestry, Environmental Engineering and Land Based Economics (DEIAFA) Mechanics Section, Turin University, via Leonardo da Vinci 44, 10095 Grugliasco, TO, Italy e-mail: [email protected]
Keywords Anaerobic digestion . Agricultural by-products . Organic waste . Biogas . Energy potential
Introduction Biogas plants across Europe are mainly fed with animal effluents and dedicated energy crops [1]. However, as the number of biogas plants has increased over the past decade, the quantity of energy crops dedicated to energy production rather than animal feed has also increased. This shift to energy crops may cause serious problems for both the agricultural sector and the world economy [2] by incentivizing producers in a way that upsets the delicate balance the world maintains to feed all peoples. Consequently, research on new substrates for anaerobic digestion plants (ADPs) is necessary. Currently, large quantities of agro-industrial by-products with no commercial value are destined for landfills, or, in the case of cereal straws and maize stalks, abandoned in fields after harvest. Energy production from agricultural by-products is generally combustion-based as their low water content (12– 1
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