Could biosolids contribute to zero carbon emissions?

Biosolids from Bolivar Wastewater Treatment Plant SCIENCE AND TECHNOLOGY
Biosolids from Bolivar Wastewater Treatment Plant.

The use of biosolids from sewage on farms could help Australia reduce carbon emissions – but only if environmental policies are updated to encourage more research and development into the area, according to the work of a UniSA PhD student.

Norman (Chin How) Goh is in the final stages of completing his PhD working on biosolids and its possible application to offsetting carbon emissions.

When sewage is treated in wastewater treatment plants, it is separated into solids and liquids so the safe, usable resources like recycled wastewater and biosolids can be used for agriculture.

Biosolids are organic matter recycled from sewage, similar to manure and rich in nutrients suitable for plant growth.

Norman says biosolids are unique as they contain high levels of stable organic carbon.

“Scientists theorise that when biosolids are used in agriculture, some of the organic carbon begins to accumulate over time and with repeated applications over the years, the carbon becomes stored as part of the soil,” he says.

“This therefore has the potential to lock-up biosolid carbon and may help us in combat climate change.”

Norman has analysed the numbers behind the science to see if in real-world situations, using biosolids in agriculture can actually result in soil carbon sequestration (effectively locking the carbon in the soil), enough to be economically and environmentally viable.

“Unfortunately the answer is not with the current rates of application and within the current economic climate,” he says.

Norman says that Australia’s carbon credit policy needs to catch up with the research, so that the benefits of using biosolids are fully recognised. In addition, biosolids need to be used continuously, and potentially on a much bigger scale, to make a difference.

“This is an over simplistic explanation but essentially, the policy and science behind carbon crediting from biosolids soil carbon sequestration is still limited. We can get there but we need a bit more scientific research and stronger environmental policies to get us over the line.”

With strong support from the water industry in offsetting carbon emissions, biosolids may be the key as the use in agriculture does offset carbon emissions, in the form of nutrients.

“Instead of using traditional chemical fertilisers produced with high energy requirements, biosolids can be a good organic substitute. In fact, it is already happening but we are still a few years away from biosolids being seen as a true commodity and being valued as a means of offsetting our emissions.

“My research is unique as it has shown what areas we need to work on to make this viable. It is a controversial subject and confusing for policy makers, industry and the general public but my work hopefully clears some of that up.”

The research was supported by the Cooperative Research Centre for Low Carbon Living, a national research and innovation hub that seeks to enable a globally competitive low carbon built environment sector, supported by the Cooperative Research Centres (CRC) programme. More information on the biosolids CRC project can be found on the CRC website. For further detail, contact Dr Michael Short or Professor Chris Saint.