Anaerobic digestion (AD) can play an important role in achieving renewable goals set within the Netherlands which strives for 40 PJ bio-energy in the year 2020. This research focusses on reaching this goal with locally available biomass waste flows (e.g. manures, grasses, harvest remains, municipal organic wastes). Therefore, the bio-energy yields, process efficiency and environmental sustainability are analyzed for five municipalities in the northern part Netherlands, using three utilization pathways: green gas production; combined heat and power; and waste management. Results indicate that the Dutch goal cannot be filled through the use of local biomass waste streams, which can only reach an average of 20 PJ. Furthermore renewable goals and environmental sustainability do not always align. Therefore, understanding of the absolute energy and environmental impact of biogas production pathways is required to help governments form proper policies, to promote an environmentally and social sustainable energy system.
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The dairy sector in the Netherlands aims for a 30% increase in efficiency and 30% carbon dioxide emission reduction compared to the reference year of 1990, and a 20% share of renewable energy, all by the year 2020. Anaerobic Digestion (AD) can play a substantial role in achieving these aims. However, results from this study indicate that the AD system is not fully optimized in combination with farming practices regarding sustainability. Therefore, the Industrial Symbiosis concept, combined with energy and environmental system analysis, Life Cycle Analysis and modeling is used to optimize a farm-scale AD system on four indicators of sustainability (i.e., energy efficiency, carbon footprint, environmental impacts and costs). Implemented in a theoretical case, where a cooperation of farms share biomass feedstocks, a symbiotic AD system can significantly lower external energy consumption by 72 to 92%, carbon footprint by 71 to 91%, environmental impacts by 68 to 89%, and yearly expenditures by 56 to 66% compared to a reference cooperation. The largest reductions and economic gains can be achieved when a surplus of manure is available for upgrading into organic fertilizer to replace fossil fertilizers. Applying the aforementioned symbiotic concept to the Dutch farming sector can help to achieve the stated goals indicated by the Dutch agricultural sector for the year 2020.
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Biogas plays an important role in many future renewable energy scenarios as a source of storable and easily extracted form of renewable energy. However, there remains uncertainty as to which sources of biomass can provide a net energy gain while being harvested in a sustainable, ecologically friendly manner. This study will focus on the utilization of common, naturally occurring grass species which are cut during landscape management and typically treated as a waste stream. This waste grass can be valorized through co-digestion with cow manure in a biogas production process. Through the construction of a biogas production model based on the methodology proposed by (Pierie, Moll, van Gemert, & Benders, 2012), a life cycle analysis (LCA) has been performed which determines the impacts and viability of using common grass in a digester to produce biogas. This model performs a material and energy flow analysis (MEFA) on the biogas production process and tracks several system indicators (or impact factors), including the process energy return on energy investment ((P)EROI), the ecological impact (measured in Eco Points), and the global warming potential (GWP, measured in terms of kg of CO2 equivalent). A case study was performed for the village of Hoogkerk in the north-east Netherlands, to determine the viability of producing a portion of the village’s energy requirements by biogas production using biomass waste streams (i.e. common grass and cow manure in a co-digestion process). This study concludes that biogas production from common grass can be an effective and sustainable source of energy, while reducing greenhouse gas emissions and negative environmental impacts when compared to alternate methods of energy production, such as biogas produced from maize and natural gas production.
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A major challenge for the Netherlands is its transition to a sustainable society: no more natural gas from Groningen to prevent earthquakes, markedly reduced emissions of the greenhouse gas carbon dioxide to stop and invert climate change, on top of growth of electricity in society. Green gas, i.e. biogas suitable for the Dutch gas grid, is supposed to play a major role in the future energy transition, provided sufficient green gas is produced. This challenge has been identified as urgent by professional, academic and private parties and has shaped this project. In view of the anticipated pressure on biomass (availability, alternative uses), the green gas yield from difficult-to-convert biomass by anaerobic digestion should be improved. As typically abundant and difficult-to-convert biomass, grass from road verges and nature conservation areas has been selected. Better conversion of grass will be established with the innovative use of new consortia of (rumen) micro-organisms that are adapted or adaptable to grass degradation. Three-fold yield increase is expected. This is combined with innovative inclusion of oxygen in the digestion process. Next green hydrogen is used to convert carbon dioxide from digestion and maximize gas yield. Appropriate bioreactors increasing the overall methane production rate will be designed and evaluated. In addition, new business models for the two biogas technologies are actively developed. This all will contribute to the development of an appropriate infrastructure for a key topic in Groningen research and education. The research will help developing an appropriate research culture integrated with at least five different curricula at BSc and MSc level, involving six professors and one PhD student. The consortium combines three knowledge institutes, one large company, three SMEs active in biogas areas and one public body. All commit to more efficient conversion of difficult-to-convert biomass in the solid body of applied research proposed here.
