What was it all about?

In 2019, this investment explored alternative sources of carbon for use in mushroom compost production by looking at the physical and chemical properties, compost quality, relative benefits and potential risks of a range of possible carbon sources. Wheaten straw is currently the most common carbon source used in mushroom compost production but is predicted to become more difficult to acquire and more expensive over time, so this investment was all about future-proofing the mushroom industry.

The research team investigated alternative carbon sources that could partially or completely substitute for wheaten straw in mushroom compost substrate, with the aim of improving business security for mushroom growers.

The research team conducted a literature review, industry consultation, and discussions with global researchers to develop a list of potential alternative carbon sources. Each was considered for its physical and chemical characteristics, plus its effects on composting and mushroom yields. Other assessment factors included consistency of supply volumes, purchase price, transportation, health and safety issues, and compliance to regulations and quality standards.

Four carbon sources were identified with the appropriate physiochemical properties plus viable cost and availability, which were wastepaper, forestry waste, corn stover, and sugar bagasse.

Both born stover and sugar appear to be ideal for use as a substitute for wheaten straw, however transport distances may pose a logistical hurdle. The use of wastepaper (either shredded or soft-mixed) in composting is limited by its physical properties, however it could replace around 20 per cent of wheaten straw in compost without negatively impacting mix porosity. 

The researchers found that wheaten straw has unique properties that are difficult to replicate, and materials with good properties for composting that were also abundantly available were difficult to identify. The alternative carbon sources are also subject to similar price-competition due to their use in other industries, especially the feedstock industry.

The research team shared its results with the mushroom industry, as fully investigating the potential use of other carbon sources for complete or partial substitution needs to consider what changes to the conventional production system are required, including composting systems and culture practices for growing A. bisporus.

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You can read about the project in these articles featured in the Australian Mushroom Journal:

• Compost substrate alternatives being considered, published on page 22 of the Australian Mushrooms Journal, Edition 3 2019
• Feasibility of compost substrate alternatives: a project update, published on page 30 of the Australian Mushrooms Journal, Edition 2 2020.