Abstract
Global warming and climate change are imminent threats to the future of humankind. A shift from the current reliance on fossil fuels to renewable energy is key to mitigating the impacts of climate change. Biological raw materials and residues can play a key role in this transition through technologies such as anaerobic digestion. However, biological raw materials must also meet other existing food, feed and material needs. Green biorefinery is an innovative concept in which green biomass, such as grass, is processed to obtain a variety of protein products, value-added co-products and renewable energy, helping to meet many needs from a single source. In this study, an analysis has been conducted to understand the renewable energy potential of green biorefinery by-products and residues, including grass whey, de-FOS whey and press cake. Using anaerobic digestion, the biogas and biomethane potential of these samples have been analyzed. An analysis of the fertiliser potential of the resulting digestate by-products has also been undertaken. All the feedstocks tested were found to be suitable for biogas production with grass whey, the most suitable candidate with a biogas and biomethane production yield of 895.8 and 544.6 L/kg VS, respectively, followed by de-FOS whey and press cake (597.4/520.3 L/kg VS and 510.7/300.3 L/kg VS, respectively). The results show considerable potential for utilizing biorefinery by-products as a source for renewable energy production, even after several value-added products have been co-produced.
Highlights
Climate change and interrelated environmental challenges represent the most eminent issues that threaten the future of the humankind
The paper has investigated and discussed the biogas and biomethane potential of three processing co-products and sidestreams resulting from a green biorefinery process based on perennial ryegrass as feedstock, namely press cake, whey and de-FOS whey
The analysis, taking into account key parameters such as the C:N ratio, C/S ratio, biodegradability of volatile solids, potassium and phosphorous levels, indicates that all three feedstocks are of suitable composition for use in anerobic digestion, including for mono-digestion
Summary
Climate change and interrelated environmental challenges represent the most eminent issues that threaten the future of the humankind. The energy sector is responsible for 75% of the total greenhouse emissions in the EU. Ensuring a greater contribution of renewable sources of energy across all sectors has been identified as a key building block for achieving climate and energy objectives. The Renewable Energy Directive (2009/28/EC) is a legal framework supporting renewable energy integration across all sectors in the EU [2]. This directive set out an overall target of 20% renewable energy integration by 2020, with binding contributory targets for each of the individual states. Ireland failed to meet its 2020 Renewable Energy Directive Target of 16%, falling short in
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