A Norwegian study has revealed that recycled food waste processed in biogas plants may harbor pharmaceutical residues. However, fungi cultivated in biogas digestate show minimal absorption of these contaminants.

In her doctoral thesis, Astrid Solvåg Nesse, a research scientist at the Norwegian Institute of Bioeconomy Research, collected and examined biogas digestates of food waste and sewage sludge from all public biogas plants in Norway.

“What I have done is investigate the types of pollutants that may be found in the digestate of food waste and compare it with the content in the digestate of sewage sludge. I have also examined the risk of using contaminated biogas digestate to produce edible fungi,” says Nesse.

Challenge for sustainable biogas production
According to the article published innclick="updateothersitehits('Articlepage','External','OtherSitelink','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','339239','https://pubs.acs.org/doi/full/10.1021/acs.jafc.2c03790', 'article','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues');return no_reload();"> Journal of Agricultural and Food Chemistry, recycling organic waste for biogas production is important for achieving a circular economy and reducing raw material demand and waste production, thereby curbing greenhouse gas emissions.

The processing of food waste or sewage sludge in biogas plants yields energy-rich biogas and generates a valuable byproduct known as biogas digestate or slurry. This digestate serves as fertilizer in agriculture and nourishes soil microorganisms, enhancing soil structure and health.

“Recycled organic material in the form of biogas digestate can be effectively used as fertilizer, as long as it does not contain substances we prefer not to have in the soil,” Nesse remarks.

One problem with using biogas digestate as fertilizer is that it might have pollutants like leftover medicines and chemicals. These pollutants can get absorbed by plants or seep into rivers and lakes, which could harm the organisms living in and around the soil.

The digestate for per- and polyfluoroalkyl substances (PFAS) can also be found in the waste. They are extensively utilized for theirnclick="updateothersitehits('Articlepage','External','OtherSitelink','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','339239','https://www.foodingredientsfirst.com/news/duty-to-disclose-californias-attorney-general-gives-pfas-producers-forever-chemicals-reminder.html', 'article','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues');return no_reload();"> grease-repellent qualities in Teflon pans, water-repellent textiles and paper-based food packaging. Evidence highlights their nclick="updateothersitehits('Articlepage','External','OtherSitelink','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues','339239','https://www.packaginginsights.com/news/us-bill-targets-nationwide-pfas-ban-as-research-points-to-human-health-dangers.html', 'article','Edible mushroom cultivated in recycled food waste show minimal absorption of pharmaceutical residues');return no_reload();">potential hazards to both human health and the environment.

“PFAS are highly stable in the environment. Our analyses showed that for most PFAS, there were higher concentrations in biogas digestate from sewage sludge than in that of food waste,” Nesse says.

Utilizing contaminated waste for cultivation
The scientist undertook several growth experiments with digestate cultivated fungi. The objective was to assess the viability of utilizing contaminated recycled organic waste through edible mushroom cultivation.

This study marks the first investigation into the uptake of emerging and ultra-short chain PFAS by mushrooms, with the findings generally suggesting minimal accumulation of PFAS.

“Initially, biogas digestate is suitable for cultivating mushrooms and other edible fungi. However, it is important to control how much of the contaminants in the digestate end up in the mushrooms,” Nesse remarks.

The results disclosed that the fungi absorbed very little of both pharmaceuticals and perfluorinated substances. Rather, these substances remained in the growth medium. According to Nesse, there was a substantial decrease in the concentration of contaminants in the growth medium as time progressed.

“It is, therefore, possible to produce edible mushrooms on contaminated digestate, while simultaneously reducing the contamination in the digestate. The used growth medium can then be well-suited for further use as fertilizer, for example, in agriculture,” she concludes.