The effect of particle size and thermal pre-treatment on the methane yield of four agricultural by-products

Abstract

One way to optimize methane production in anaerobic digestion plants is to substitute ligno-cellulosic by-products for crops traditionally used as energy sources. However, using these by-products requires introduction of a pre-treatment system to minimize energy input and maximize energy output for an improved net energy equation. In this study, four agricultural byproducts (wheat, barley, rice straw and maize stalks) underwent various mechanical and thermal treatments prior to anaerobic digestion including particle size reduction to 5.0, 2.0, 0.5, and 0.2 cm and heat application to 90 °C and 120 °C. Mechanical pre-treatment increased byproduct methane yields more than 80%; thermal pre-treatment improved yields more than 60% for wheat and barley straw. Pre-treating wheat straw improved methane yields most, regardless of whether the method was thermal or mechanical. An electric net energy balance was also completed to analyze the feasibility of the pre-treatments according to input and output of energy.

Soybean Straw, Corn Stover and Sunflower Stalk as Possible Substrates for Biogas Production in Croatia: A Review

“…In their pilot-scale experiment, Schell and Harwood 66 showed that lignocellulose particle size of 1 to 2 mm is effective for hydrolysis. Menardo et al 67 conducted various mechanical and thermal treatments prior to AD of four agricultural byproducts. An net electrical energy balance was also completed to analyze the feasibility of the pretreatments according to energy input and output.…”

Enhanced Soluble Protein and Biochemical Methane Potential of Apple Biowaste by Different Pretreatment

“…Agro-industrial byproducts and residues are often used as the broadcast source of the substrate for anaerobic biotransformation to biogas, which suggests that byproduct substrates could be alternatives to energy crops in anaerobic digestion plants (Menardo et al 2012). Although biomass energy is more costly than fossil fuel-derived energy, trends to limit carbon dioxide and other emissions through emission regulations, carbon taxes, and subsidies of biomass energy would make it cost competitive (Chynoweth et al 2001;Charters 2001), even when low-cost treatment, due to high energy recovery and environmentally friendly are taken into consideration (Ferreira et al 2013).…”

Anaerobic Digestion

“…hectare in Germany [35]. With increasing competition for land and food, together with natural resources such as water and nutrients, the AD sector has typically focused on deriving energy from wastes and residues [6]. However, a number of second-generation energy crops are emerging that have shown good potential as feedstocks for bio-energy and particularly AD.…”

“…Treatments at temperatures of 130, 150 and 170 • C all led to sludge reduction, with higher temperatures leading to a reduction in volatile solids of up to 80% compared to controls. Menardo [6] noted increased methane yields of up to 40% when applying 90 • C thermal pre-treatment to wheat and barley straw; however, negligible improvements were noted for maize straw and rice stalks having received the same …”