Green proteins: An energy‐efficient solution for increased self‐sufficiency in protein in Europe

Abstract

The heavy reliance of the livestock industry of the European Union (EU) on feed protein imports has initiated a transition to alternative protein sources such as grass proteins. Green biorefineries (which process grass into protein and other related bio-products) are gaining interest in the EU as the EU searches for ways to cut its import of feed proteins, to reduce its reliance on fossil fuels, and to combat climate change. However, the vulnerability of green biorefineries to fossil energy constraints has not been studied. We estimated the energy conversion efficiencies (EE) and the energy return on investment (EROI) of bio-products from standalone (SGBR) and integrated grass refinery (IGBR) systems using scenario and energy analysis. The base scenario assumes an SGBR that processes grass into protein, fiber, and brown juice. The three IGBR scenarios assume that grass is processed into protein, fiber, and biomethane (Scenario 1); into protein, fiber, heat, and electricity (Scenario 2); or into protein, fiber, heat, and biomethane (Scenario 3). We found that the EE of the IGBR (83%-85%) largely exceeded that of the SGBR (77%) in all cases. Energy returns on investment were lower for grass than for clover-grass because of the high fertilizer needs of the former. The standard EROIs (EROI std ) for grass protein ranged from 1.6 to 5.4 over the various feedstocks and scenarios evaluated. The EROI std decreased when the system boundary was expanded to the point of use (EROI pou ), or when they were adjusted for quality (EROI qly ). Other bioproducts from both SGBR and IGBR also had high EROI std , and showed similar patterns to that of grass protein (i.e., EROI std > EROI pou > EROI qly ). Although Scenario 1 had a high EE relative to the base scenario, its heavy reliance on auxiliary energy inputs reduced the EROIs of its products. Our analysis showed the strong impacts of brown-juice recycling in the energy performance of green biorefinery. It thus deserves close attention when designing and implementing a green biorefinery in a given region. 606S Njakou Djomo et al.Modeling and Analysis: Energy Balance of Green Protein With favorable economic conditions, green biorefineries could contribute to the reduction of food and energy insecurity in Europe in a sustainable way.

Large-scale deployment of grass in crop rotations as a multifunctional climate mitigation strategy

“…A prerequisite for widespread deployment of in-rotation grass cultivation is a demand for products that can be produced from the grass biomass. There is an increasing interest in biorefineries, processing grass-clover mixes into protein concentrate and a multitude of other products, e.g., feed, fibers, heat, power, and biofuels 24 . Pig feeding trials in Denmark show that extracted grass protein with a high protein content (47% DM) can substitute soymeal without any adverse effects on animal performance and meat quality 44 .…”

“…In other places, incentives such as payments for soil carbon sequestration and other environmental benefits may be needed 16 . Investors need to be confident in the long-term economic viability of grass-based biorefineries 24 , which is likely to be influenced by the outcome of the current process following the European Commission's proposal 25 to revise the Renewable Energy Directive (RED). For example, treatment of biogas from biorefineries in the revised RED will depend on whether biogas is considered a main product or co-product of the biorefinery process.…”

Bioenergy Potential and Greenhouse Gas Emissions from Intensifying European Temporary Grasslands

“…The displacement of soy meal is particularly interesting from an environmental perspective given that soy production in Latin America is associated with (directly or indirectly) causing deforestation [88] and therefore high land use change emissions. A co-product is biogas or, if upgraded, biomethane [70]. More research is needed in order to better understand the net environmental impacts and the economic performance of grass biorefineries.…”

“…As a mixture of species is applied here, but shares and species are not defined, we make an assumption on the energy content of the grass mixture being slightly lower than the average of miscanthus, switchgrass and reed canary grass. We acknowledge that this may still be an optimistic estimate (see e.g., [70] who apply a value for a grass/clover grass = 13.5 MJ kg −1 (LHV); no indication is given though whether this is dry or fresh biomass). 2 Based on a brief literature review of recent publications on advanced bioethanol conversion, Gerssen-Gondelach et al [8] applied a grass-to-bioethanol conversion efficiency (HHV) of 35% for the short term.…”

Solid Biomass Energy Potential as a Development Opportunity for Rural Communities

“…Therefore, it was assumed that three instead of two cuts could be obtained from 5% of the meadows, and the surplus produced amounting to 2 Mg ha −1 year −1 could be used as energy feedstock [75,76]. The potential of hay from meadows was calculated with the lower heating value taken as 13.5 GJ Mg −1 [77] (11). The assumed yield was regarded as the amount of hay obtained from mowing and collection, including possible baling.…”