Opinions on biogas in organic farming

The application of biogas technologies in organic farming involves many considerations: Benefits like improved fertilizer supply and fossil fuel savings are opposed to concerns about economical risks and incompliance with organic principles. A questionnaire developed by Risø DTU gives an idea about some Danish stakeholders’ perceptions of benefits and drawbacks

Evaluation of Novel Inoculation Strategies for Solid State Anaerobic Digestion of Yam Peelings in Low-Tech Digesters

The operation of household scale anaerobic digesters is typically based on diluted animal dung, requiring stabled livestock and adequate water availability. This excludes many rural households in low-income countries from the benefits of a domestic biogas digester. Solid state anaerobic digestion (SSAD) can be operated with low process water demands, but the technology involves operational challenges, as e.g., risk of process acidification or low degradation rates. This study aimed at developing simple methods to perform SSAD of yam peelings in low-tech applications by testing different inoculation strategies and evaluating the necessity of dung addition as a supportive biomass. In initial lab scale trials 143 ± 4 mL CH4/g VS (volatile solids) were obtained from a mixture of yam peelings and dung digested in a multi-layer-inoculated batch reactor. In a consecutive incubation cycle in which adapted inoculum was applied, bottom inoculated digesters loaded without dung reached a yield of 140 ± 16 mL CH4/g VS. This indicates that SSAD of yam peelings is possible with simple inoculation methods and dung addition is unnecessary after microbial adaptation. A comparison with a conventional fixed dome digester indicated that SSAD can reduce process water demand and the digester volume necessary to supply a given biogas demand

Field emissions of N2O during biomass production may affect the sustainability of agro-biofuels

Field emissions of N2O during cultivation of bioenergy crops may counterbalance a considerable part of the avoided fossil CO2 emissions that are achieved by fossil fuel displacemen

Combination of ensiling and fungal delignification as effective wheat straw pretreatment

BACKGROUND: Utilization of lignocellulosic feedstocks for bioenergy production in developing countries demands competitive but low-tech conversion routes. White-rot fungi (WRF) inoculation and ensiling are two methods previously investigated for low-tech pretreatment of biomasses such as wheat straw (WS). This study was undertaken to assess whether a combination of forced ensiling with Lactobacillus buchneri and WRF treatment using a low cellulase fungus, Ceriporiopsissubvermispora, could produce a relevant pretreatment effect on WS for bioethanol and biogas production. RESULTS: A combination of the ensiling and WRF treatment induced efficient pretreatment of WS by reducing lignin content and increasing enzymatic sugar release, thereby enabling an ethanol yield of 66 % of the theoretical max on the WS glucan, i.e. a yield comparable to yields obtained with high-tech, large-scale pretreatment methods. The pretreatment effect was reached with only a minor total solids loss of 5 % by weight mainly caused by the fungal metabolism. The combination of the biopretreatments did not improve the methane potential of the WS, but improved the initial biogas production rate significantly. CONCLUSION: The combination of the L. buchneri ensiling and C. subvermispora WRF treatment provided a significant improvement in the pretreatment effect on WS. This combined biopretreatment produced particularly promising results for ethanol production. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13068-016-0437-x) contains supplementary material, which is available to authorized users

Relating N2O emissions from energy crops to the avoided fossil fuel-derived CO2 – a study on bioethanol and biogas produced from organically managed maize, rye, vetch and grass-clover

Field emissions of N2O during cultivation of bioenergy crops may counterbalance a considerable part of the avoided fossil CO2 emissions that are achieved by fossil fuel displacement

Greenhouse gas emissions from cultivation of energy crops may affect the sustainability of biofuels

Field emissions of N2O during cultivation of bioenergy crops may counterbalance a considerable part of the avoided fossil CO2 emissions that are achieved by fossil fuel displacemen