Environmental and energy system analysis of bio-methane production pathways: A comparison between feedstocks and process optimizations. (15th December 2015)

• Record Type: Journal Article
• Authors: Pierie, F.; van Someren, C.E.J.; Benders, R.M.J.; Bekkering, J.; van Gemert, W.J.Th.; Moll, H.C.
• Is Part Of: Applied energy. Volume 160(2015:Dec. 15)
• Page Start: 456
• Page End: 466
• Publication Date: 2015-12-15
• Subjects: Anaerobic digestion -- Green gas -- Bio-methane -- Life cycle analysis (LCA) -- Energy crops -- Organic waste; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.09.066
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Using local waste feedstock and optimization improves environmental sustainability. Optimization favors waste feedstocks. Transport distances should not exceed 150 km. The produced energy should be used for powering the green gas process first. The AD process should be used primarily for local waste treatment. Abstract: The energy efficiency and sustainability of an anaerobic green gas production pathway was evaluated, taking into account five biomass feedstocks, optimization of the green gas production pathway, replacement of current waste management pathways by mitigation, and transport of the feedstocks. Sustainability is expressed by three main factors: efficiency in (Process) Energy Returned On Invested (P)EROI, carbon footprint in Global Warming Potential GWP(100), and environmental impact in EcoPoints. The green gas production pathway operates on a mass fraction of 50% feedstock with 50% manure. The sustainability of the analyzed feedstocks differs substantially, favoring biomass waste flows over, the specially cultivated energy crop, maize. The use of optimization, in the shape of internal energy production, green gas powered trucks, and mitigation can significantly improve the sustainability for all feedstocks, but favors waste materials. Results indicate a possible improvement from an average (P)EROI for all feedstocks of 2.3 up to an average of 7.0 GJ/GJ. The carbon footprint can potentially be reduced from an average of 40 down to 18 kgCO2 eq/GJ. The environmental impact can potentially be reduced from an average of 5.6 down to 1.8 Pt/GJ. Internal energy production proved to be the most effective optimization. However, the use of optimization aforementioned will result in les green gas injected into the gas grid as it is partially consumed internally. Overall, the feedstock straw was the most energy efficient, where the feedstock harvest remains proved to be the most environmentally sustainable. Furthermore, transport distances of all feedstocks should not exceed 150 km or emissions and environmental impacts will surpass those of natural gas, used as a reference. Using green gas as a fuel can increase the acceptable transportation range to over 300 km. Within the context aforementioned and from an energy efficiency and sustainable point of view, the anaerobic digestion process should be utilized for processing locally available waste feedstocks with the added advantage of producing energy, which should first be used internally for powering the green gas production process.