Potential of anaerobic digestion for mitigation of greenhouse gas emissions and production of renewable energy from agriculture: barriers and incentives to widespread adoption in Europe

Abstract

The paper considers the role of anaerobic digestion in promoting good agricultural practice on farms and the contribution this would make to reducing the environmental impacts associated with manure management. There are no regulatory drivers to promote the use of digestion in Europe, and the technology has only been widely adopted where economic drivers and coherent policies have been implemented at a national level. These measures have included direct subsidy on the energy price paid for "green electricity", and exemption of tax when biogas is used as a vehicle fuel. In those countries where financial incentives are not available or where a financial penalty is incurred through the regulatory regime, the uptake of digestion has been poor. Even with subsidies, digestion of animal manures as a single substrate is not common, and countries with successful schemes have achieved this either by permitting the import of wastes onto the farm or offering bonus subsidies for the use of energy crops. Both of these measures improve the energy efficiency of the process by increasing the volumetric methane production, although concerns are expressed that attention could concentrate on energy production at the expense of improving manure management.

Characterization of Solid Digestates: Part 2, Assessment of the Quality and Suitability for Composting of Six Digested Products

“…All the digestates characterized here contained less TKN than other digestates already studied [33][34][35]. The digestates characterized in this study also appeared to be less concentrated in NH 4 ? as it represented only 30% of TKN on average and ammonium content was under the detection threshold for WWTS 2 digestate.…”

“…TKN was measured after mineralization (using Gerhardt Kjeldhaltherm TZ device) of the dried ground samples within a strong acid medium followed by steam distillation and titrimetric determination (using a Gerhardt automatic Vapodest 50 device) according to standardized analytical method [17]. NH 4 ? was also determined by steam distillation and titrimetric determination (using Büchi 324 distiller and Metrohm titrator) on non-mineralized aqueous extracts of the wastes [17].…”

“…The high adaptability of the digestion process allows the treatment of a wide range of organic wastes by this technology. Denmark played an important role in the development of agricultural AD with the settlement in 1988 of the Biogas Action Program [4]. In 1992, the Italian Government regulated incentives for self-production of electric energy from biomass, encouraging thus AD of organic wastes.…”

Energetic and environmental benefits of co-digestion of food waste and cattle slurry: A preliminary assessment

“…This low energy potential means that anaerobic digestion of manures and slurries from dairy herds has never been economically attractive in Europe, as confirmed by the very small number of digesters found on farms of this type. There are, however, significant environmental benefits from digesting cattle slurry which can make a major contribution to EU and UK government targets for GHG emissions (Banks et al, 2007). Greenhouse gas emissions from manure management in the EU 27 in 2008 were estimated as 50.26 million tonnes CO 2 equivalent, of which dairy cattle contributed 21% (EEA, 2010).…”

“…This may again restrict the installation of digesters on farms, where suitable electricity grid connections may not be available and the cost of upgrading the connection to allow electricity export is often prohibitive. The above circumstances, combined with UK waste management infrastructure, logistics and contractual arrangements, and regulatory requirements all work against the installation of smaller-scale co-digestion plant on farms (Banks et al, 2007). Yet without the input of a high-energy waste material, the volumetric gas productivity of farm-based digesters fed solely on manures and slurry is unlikely to be economically viable, and the energy potential and environmental benefits of digesting these substrates will be lost.…”