In 2022, global beer production reached nearly 1.9 billion hectolitres, generating vast amounts of brewer’s spent grains (BSG) as by-products. While BSG’s high organic content and moisture make it an attractive low-cost animal feed, improper disposal, particularly in regions with minimal livestock industries, often leads to waste or environmental impact.
As one of the largest beer and food producers globally, Brazil faces the challenge of managing significant quantities of industrial residues, primarily from breweries and agricultural activities. Recent research published in Nature, focusing on the potential reuse of these residues, highlights two major sustainable applications: mushroom cultivation and mycelium-based biocomposites, advancing waste valorization and the circular economy.
Image courtesy: Brewers Association
Brewer’s Spent Grains in Mushroom Cultivation
Researchers found that Brazil’s abundant brewer's spent grains (BSG) hold substantial promise for Pleurotus sajor-caju (oyster mushroom) cultivation, especially when combined with locally available banana or peach palm leaves. The northern Santa Catarina region, known for its thriving food and brewing industries, produces large amounts of these agro-residues, presenting an ideal testing ground for sustainable substrate combinations. Key findings include:
Direct Use of Fresh BSG: Mushrooms cultivated on fresh or dried BSG performed similarly, eliminating the need for additional processing time and costs. This could allow breweries to quickly transfer BSG from production to mushroom cultivation, streamlining the entire process.
Enhanced Productivity with Mixed Substrates: When BSG was combined 1:1 with either banana or peach palm leaves, mushroom productivity increased, reaching 0.41 g/day and 0.38 g/day, respectively. These mixtures surpassed the results of single-substrate cultivation, suggesting that banana and peach palm leaves provide additional nutritional benefits.
Nutritional Value and Safety: The cultivated mushrooms are rich in sugars, low in sodium, and serve as valuable sources of phosphorus without detectable levels of harmful heavy metals (mercury and lead). This supports the viability of using BSG-mixed substrates for high-quality, nutritious mushroom production.
From Harvest Residue to Mycelium-Based Composites
After mushroom harvest, the residual substrate undergoes a transformation into mycelium-based composites, highlighting an efficient dual-use pathway that extends resource utility. This application addresses the need for sustainable alternatives to synthetic materials and demonstrates a clear path forward for Brazil’s industrial waste management:
Enhanced Composite Strength: Residual substrates left after mushroom growth exhibit improved mechanical properties, including compressive strength (0.04 MPa) and density (242 kg/m³). These qualities indicate that post-harvest substrates are better suited for creating durable, structurally resilient biocomposites than unprocessed substrates.
Humidity Resistance: The residual substrate’s lower water absorption capacity makes the resulting composites resistant to humidity, a critical property for packaging, construction, and other potential applications in humid or high-moisture environments.
Diagram of the mycelium-based composites process manufacturing
Circular Bioeconomy in Action: Brazil’s Role in Sustainable Innovation
By leveraging readily available agricultural residues, Brazil stands to not only improve waste management but also contribute to the growing bio-based materials market. This research underscores the synergistic benefits of combining traditional mushroom cultivation with innovative biocomposite development:
Reduced Dependence on Synthetic Materials: Mycelium-based composites, made from local residues, could replace plastics, foams, and other synthetic materials in industries such as packaging, construction, and automotive. The research demonstrates that Brazil can capitalize on its natural resources to support a sustainable circular economy while reducing environmental impacts.
Resource Efficiency and Cost-Effectiveness: The study's finding that fresh BSG performs comparably to dried BSG has substantial economic implications. The ability to use unprocessed residues means breweries can avoid the costs associated with drying and storing BSG, further enhancing the feasibility of this approach.
Future Directions: Expanding Applications of Mycelium-Based Composites
To refine the application of these sustainable materials, future studies will assess additional physical properties—such as impact resistance, thermal conductivity, and acoustic absorption—needed to understand their potential use across diverse industries. Researchers also aim to explore Pleurotus sajor-caju’s potential as an antimicrobial agent for intelligent packaging solutions, a feature that could appeal to Brazil’s robust food production and export sectors.
By repurposing industrial byproducts into high-value products, Brazil’s industries could become leaders in resource-efficient, circular economy practices, setting a precedent for global sustainability. This dual-use model not only extends the life cycle of agricultural residues but also aligns with Brazil’s need for environmentally conscious material solutions, promoting the country as an innovator in bio-based technology