Prospective life cycle assessment of brewers’ spent grain valorisation via edible mushroom cultivation

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Poster Number:  12 

Main Presenter:    Elina Dace 

Co-Authors:   Eduards Teodors Mincis     Janis Liepins                                          

Brewers’ spent grain (BSG) is among the most abundant by-products of the food industry, with approximately 0.65 million tonnes generated annually in Europe. Currently, BSG is mainly used as livestock feed or as a substrate for biogas production. However, breweries, particularly small and medium-sized enterprises, are increasingly seeking locally feasible valorisation pathways that provide environmental and economic benefits. Cultivation of edible mushrooms on BSG represents a promising option, yet its life cycle environmental performance remains insufficiently explored.
This study assesses the prospective life cycle impacts of growing edible mushrooms on BSG combined with various supplements at laboratory and pilot scales. BSG was sourced from a small-scale brewery in Latvia. Six mushroom species (Pleurotus ostreatus, Pleurotus eryngii, Ganoderma lucidum, Hypsizygus tessellatus, Lentinula edodes, Cordyceps militaris) and four supplements (straw, gypsum, coffee grounds, and saponin) were experimentally tested. Based on substrate colonisation rates and yields, Pleurotus ostreatus and Pleurotus eryngii were identified as the most promising species, with the highest fruiting body production achieved using BSG mixed with straw and gypsum.
A prospective cradle-to-grave life cycle assessment was conducted using EASETECH v3.6.0 and inventory data from ecoinvent v3.10.1 (apos) and Agribalyse v3.2. The functional unit was 1000 kg of fresh BSG. BSG was modelled as burden-free at the point of entry. Environmental impacts were calculated using the Environmental Footprint method (EF v3.1 no LT) across 16 impact categories. Two mushroom cultivation scenarios (P. ostreatus and P. eryngii) were compared with a business-as-usual reference scenario in which BSG is transported and used as cattle feed. In all scenarios, harvested mushrooms were assumed to substitute conventionally produced Agaricus bisporus, while both BSG and myceliated BSG were assumed to substitute imported soymeal for animal feed.
All scenarios resulted in net negative overall environmental impacts (–7.77 PE for the reference scenario, –5.14 PE for P. ostreatus, and –4.58 PE for P. eryngii), mainly driven by avoided impacts from soymeal substitution, particularly freshwater ecotoxicity associated with pesticide use. The reference scenario performed best overall, as mushroom cultivation requires additional electricity, water, and supplementary materials. Between the two mushroom options, P. ostreatus showed better performance due to higher quantities of residual mycelium and a shorter cultivation cycle.
Future research should focus on determining the nutritional composition of myceliated BSG (especially protein content) to better quantify feed substitution potentials and strengthen the robustness of environmental benefit estimates.

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