Abstract
Based on fifteen European plant species, a statistical model for the estimation of the anaerobic biodegradability of plant material was developed. We show that this new approach represents an accurate and cost-effective method to identify valuable energy plants for sustainable energy production. In particular, anaerobic biodegradability (Bo) of lignocellulosic material was empirically found to be related to the amount of cellulose plus lignin, as analytically assessed by the van Soest method, i.e., the acid detergent fiber (ADF) value. Apart from being theoretically meaningful, the ADF-based empirical model requires the least effort compared to the other four proposed conceptual models proposed, as individual fractions of cellulose, hemicellulose, and lignin do not need to be assessed, which also enhances the predictive accuracy of the model’s estimation. The model’s results showed great predictability power, allowing us to identify interesting crops for sustainable crop rotations. Finally, the model was used to predict Bo of 114 European plant samples that had been previously characterized by means of the van Soest method.
Highlights
Closing material cycles through anaerobic digestion (AD) is an interesting alternative to provide valuable use to agricultural surplus products, agricultural residues, and energy-rich agro-industrial by-products, as well as to set aside land.The use of AD for the production of biogas from crop material and residues is a renewable and carbon-neutral technologically viable option that allows for the recirculation of nutrients and organic matter back to land, minimizing the need for external inputs and enhancing soil fertility [1,2,3]
The maximum biogas amount was reached, in most cases, after 25 days of digestion, whereas less than 1% net gas production was produced in the last 8–10 days of the experiment
Measured maximum net biogas production in all plant species was between 0.22 and 0.56 l gVS−1, with most of the species being in the range between 0.34 and 0.44 l.gVS−1
Summary
Closing material cycles through anaerobic digestion (AD) is an interesting alternative to provide valuable use to agricultural surplus products, agricultural residues, and energy-rich agro-industrial by-products, as well as to set aside land.The use of AD for the production of biogas from crop material and residues is a renewable and carbon-neutral technologically viable option that allows for the recirculation of nutrients and organic matter back to land, minimizing the need for external inputs and enhancing soil fertility [1,2,3]. Closing material cycles through anaerobic digestion (AD) is an interesting alternative to provide valuable use to agricultural surplus products, agricultural residues, and energy-rich agro-industrial by-products, as well as to set aside land. Crops and agroresidues are interesting co-digestion materials supplementing waste materials of inferior energy quality, such as animal manure, allowing us to increase the energy output per unit reactor volume [5,6]. In Europe, incentives have been given for the use of crop material as (co) substrates for anaerobic reactors, with quantified available areas being 13.2 million Ha [6,9,10]. Challenges are found when digesting this type of lignocellulosic biomass due to its relatively low methane yield, potential process instability due to volatile fatty acids (VFA) accumulation, and production of low value end-products
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