Spent mushroom compost gets a new lease of life
Mushrooms are big business: more than 1 million tonnes of mushrooms are grown each year in the EU. These crops yield a healthy, low-fat, high-protein food that is also rich in minerals and vitamins. The downside is that producing every tonne requires around 3 million tonnes of mushroom compost. This mixture of chicken manure, peat and wheat straw is only suitable for one to three harvests. Getting rid of it poses major economic and logistical problems for Europe’s farmers. The mushroom industry currently lacks adapted technological solutions to upgrade this spent compost into valuable products.
Turning waste into value
The EU-funded BIOrescue project demonstrated a sustainable biorefinery process to transform the vast majority of spent mushroom compost (as well as other types of underutilised agricultural waste) into valuable bioactive compounds and bioproducts. The industrial leader of the consortium has been one of the major mushroom producers: Monaghan Mushrooms. The novel system is supported by modern mathematical modelling tools that rapidly analyse the composition of biomass waste. With high accuracy, the innovative methodology models the composition of samples that have been previously determined by their measured near-infrared spectra. “Rapid biomass analysis is the key to a successful biorefinery process. The new advanced algorithms developed by the company CELIGNIS could make sample analysis cost less than EUR 100 per sample, one day,” notes BIOrescue project coordinator Inés del Campo, at the National Renewable Energy Centre of Spain, CENER. Project partners also developed two parallel processes for optimising biomass pretreatment. The first one, called organosolv pretreatment, is used to obtain the maximum amount of lignin, while sugars are retrieved through a thermochemical pretreatment process. What’s more, biotechnology company METGEN created patented tailored enzymatic solutions that efficiently break down the long chains of sugars and lignin polymers in the biomass compost into smaller pieces: this process makes their extraction easier compared to the use of commercial enzymes for the same purpose. “Used mushroom compost works wonders. We developed low-cost, highly concentrated biopesticides that are less toxic but equally efficient as their fossil-based counterparts on the market. In addition, the Max Planck Institute of Polymers has transformed lignin into tiny biodegradable capsules that can be employed for controlled and progressive drug release and even as a potential new plant vaccine targeting specific diseases,” adds del Campo.
A sustainable and replicable concept
From biomass analysis to conversion, innovation is driving each step of the biorefinery process. By generating low-carbon bio-based products that can be used in agriculture, BIOrescue is closing the loop towards a truly circular agri-food industry. Project partners conducted preliminary analyses to evaluate potential combinations of mushroom compost with other underutilised agricultural feedstocks. They found that wheat straw, oat straw and barley straw combine most efficiently with spent mushroom compost. Finally, they assessed the availability of these feedstocks during the entire year in different regions – a critical element towards developing local biorefinery processes. “In BIOrescue, we looked at creating a circular economy in the mushroom industry, but also saw the numerous opportunities beyond,” notes del Campo. “In that sense, our biorefinery concept will be replicable with other types of agricultural residues, and thus relevant for other industries that generate large amounts of biomass waste.”
BIOrescue, spent mushroom compost, biomass, biorefinery, agricultural residue, biopesticide, drug delivery, circular economy, agri-food