The implications of management practices on life cycle greenhouse gas emissions in biogas production.

Biogas production is seen as one of the key measures in circular economy providing several benefits for the environment. In practice, however, these benefits may not be achieved if the production is not implemented and managed in ways that reduce gaseous emissions. Thus, this study aimed at highlighting how different management practices impact the climate during the life cycle of biogas production in comparison to management without biogas production (reference).

Effect of manure co-digestion on methane production, carbon retention, and fertilizer value of digestate.

Anaerobic digestion can provide benefits not only from the perspective of renewable energy production but also in the form of fertilization effect and increased retention of C in soils after digestate application. This study consisted of two phases, where the first phase assessed the suitability of carbon-rich co-feedstocks for methane production via laboratory testing. The second phase assessed the balance and stability of C before and after anaerobic digestion by systematic digestate characterization, and by evaluating its carbon retention potential using a modeling approach.

Dynamics of microbial community in response to co-feedstock composition in anaerobic digestion.

To enable the utilization of seasonal biomasses in e.g., farm-scale biogas plants, the process should be flexible and ensure stable gas production.

Application of mathematical optimization to exploit regional nutrient recycling potential of biogas plant digestate.

Nutrients can be circulated back to agriculture from waste streams through anaerobic digestion and digestate processing. Digestate processing, however, is making slow progress as circulated nutrient products have not been cost competitive compared to fossil fertilizers and not designed from the farmer's perspective to truly match with the regional nutrient need. In this study, the aim is to assess apply mathematical optimization to the design of a cost-optimal processing route for a biogas plant's digestate to produce fertilizer products based on specified regional needs.

Changes in volatile fatty acid production and microbiome during fermentation of food waste from hospitality sector.

Due to the increasing demand for low carbon-footprint bioproducts in the markets, innovative processes technologies and products are needed. The objective of this study was to assess the quality and potential of food waste (FW) from the hospitality sector to produce volatile fatty acids (VFAs). A batch type acid fermentation system was used to study VFA production in different process conditions (a decreased pH and increased organic loading rate).

Effect of Inoculum Pretreatment on the Composition of Microbial Communities in Anaerobic Digesters Producing Volatile Fatty Acids.

Volatile fatty acids (VFAs) are intermediates in the methane formation pathway of anaerobic digestion and can be produced through the fermentation of organic wastes. VFAs have become an anticipated resource- and cost-effective way to replace fossil resources with higher added value and more versatile fuels and chemicals. However, there are still challenges in the production of targeted compounds from diverse and complex biomasses, such as urban biowastes.

A farm-scale grass biorefinery concept for combined pig feed and biogas production.

This study assessed the nutrient flows and the economic viability of a farm-scale grass biorefinery concept for a pig farm. Grass silage was separated into liquid and solid fractions; the liquid fraction was used as pig feed and the solid fraction was directed to biogas production together with pig slurry. The addition of grass to the farm's crop rotation and its use in feed and biogas production slightly increased the share of nitrogen (N) circulating within the farm (by 2%), thus decreasing phosphorus circulation by 3%.

Use of laboratory anaerobic digesters to simulate the increase of treatment rate in full-scale high nitrogen content sewage sludge and co-digestion biogas plants.

The aim of this study was to assess the effect of increasing feedstock treatment rate on the performance of full-scale anaerobic digestion using laboratory-scale reactors with digestate and feedstock from full-scale digesters. The studied nitrogen-containing feedstocks were i) a mixture of industrial by-products and pig slurry, and ii) municipal sewage sludge, which digestion was studied at 41 and 52°C, respectively. This study showed the successful reduction of hydraulic retention times from 25 and 20days to around 15days, which increased organic loading rates from 2 to 3.

Agronomic characteristics of five different urban waste digestates.

The use of digestate in agriculture is an efficient way to recycle materials and to decrease the use of mineral fertilizers. The agronomic characteristics of the digestates can promote plant growth and soil properties after digestate fertilization but also harmful effects can arise due to digestate quality, e.g.

Dynamics of microbial communities in untreated and autoclaved food waste anaerobic digesters.

This study describes the microbial community richness and dynamics of two semi-continuously stirred biogas reactors during a time-course study of 120 days. The reactors were fed with untreated and autoclaved (160 °C, 6.2 bar) food waste.

Anaerobic digestion of autoclaved and untreated food waste.

Anaerobic digestion of autoclaved (160°C, 6.2 bar) and untreated source segregated food waste (FW) was compared over 473 days in semi-continuously fed mesophilic reactors with trace elements supplementation, at organic loading rates (OLRs) of 2, 3, 4 and 6 kg volatile solids(VS)/m(3)d. Methane yields at all OLR were 5-10% higher for untreated FW (maximum 0.