Turning spent mushroom compost into biochar locks in more soil carbon
Ye P, Tang B, Chen X, Xiao R
Soil Health
If you've ever tossed spent mushroom compost on your garden beds, this research shows that processing it into biochar first instead of using it raw could trap far more carbon in your soil for the long haul.
Mushroom farms produce huge amounts of leftover growing material once the mushrooms are harvested, and scientists wanted to know the best way to turn that waste into something that helps soil hold onto carbon. They tested four versions, raw substrate, compost, hydrochar, and biochar, in two different soil types over four months. Biochar won for locking carbon away long-term, hydrochar quietly built up mineral-bound carbon, and compost was best at feeding soil microbes, with the biggest gains showing up in soils that started out carbon-poor.
Key Findings
Carbon sequestration efficiency ranked biochar > hydrochar > compost > raw spent mushroom substrate under equal carbon inputs in both soil types.
Biochar boosted particulate organic carbon the most, while hydrochar preferentially built mineral-associated organic carbon without raising microbial necromass.
Raw substrate and compost strongly increased microbial biomass, carbon use efficiency, and necromass buildup, with low-SOC soil (5.92 g/kg) showing stronger carbon gains than high-SOC soil (20.9 g/kg).
chevron_right Technical Summary
Scientists turned leftover mushroom-growing waste into three different soil amendments (compost, hydrochar, and biochar) and found biochar locked away the most carbon in soil, while compost fed soil microbes best; poor soils benefited most from any of these treatments.
Abstract Preview
Original paper
Contrasting soil carbon stabilization pathways following spent mushroom substrate valorization into compost, hydrochar and biochar.
Enhancing soil organic carbon (SOC) through exogenous organic materials (EOMs) is an important strategy for improving soil carbon storage. However, how EOM properties and initial soil SOC levels jo...
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