Containerised Pre-treatment Plant for Sterilising Organic Waste
Greenius is an SBRI project funded by the UK Deputy Prime Minister’s office to devise a pre-treatment plant for organic waste prior to use in an anaerobic digestion (AD) plant. Housed in a 30 ft shipping container, the finished plant heats the waste matter to 180 °C at 10 bar pressure to ensure thorough sterilisation.
There were a number of challenges involved in constructing a plant to satisfy the requirements of the project outline. In order to meet the throughput requirements, ohmic heaters were used because of the rapid, even heating they allow. Through several design and testing stages an outline was developed of a series of pressurised ohmic heaters sufficient to heat the waste to the required temperature.
There were also a number of safety aspects that had to be thoroughly considered, including the requirement that no waste or wash water was to enter the on-site drainage system. Safeguards were also put in place to prevent biohazard accidents such as spillages releasing bacteria.
The plant was constructed on time, on budget, and conformed to the project brief. Third-party testing of the plant output verified that campylobacter and E. coli were below detectable levels, and that the aerobic colony count was reduced to below 10 cfu/g.
The next stage of the project is to apply for a mobile waste treatment plant licence and commercialise the technology. There are significant benefits for AD biogas installations, including production of a more homogenous feedstock and the ability to use lower-grade food waste as the raw material.