What are the future applications for biosolids?
Research shows biosolids can be converted to methane, oil and electricity in high technology processes. However, these technologies are generally costly and require further investigation. Thermal processes have been developed that extract energy and generate power from sludges. For example, incinerators handle all biosolids produced in the London metropolitan area, generating more than 11 megawatts a year of electricity, but the system still requires some 17,000 tonnes of ash to be disposed of each year. An alternative is to use biosolids in cement kilns, where ash is locked into cement use.Energy recovery is a capital-intensive process, in contrast to our air-drying system, which is cost-efficient but requires a large area of land.
Energy recovery is likely to become more attractive for large treatment plants driven by:
- Value of land and proximity of residences to treatment plants
- Odour management
- Technology advances
- Regulation and public attitudes to the application of biosolids to agricultural land.
These processes are becoming more feasible with the introduction of the Federal Government's Renewable Energy Certificates program, in which organisations that produce renewable energy receive certificates for each megawatt-hour of electrical energy generated, enabling them to sell surplus certificates.
Alternatives to Biosolids
Wastewater treatment and the use of by products such as recycled water and biosolids are not the only direction forward with the issue of human waste management. There are a number of alternatives including:
Humanure: Humanure is a composting process using both human faeces and urine to produce a compost suitable for agricultural and other purposes. As it only uses the faeces and urine and paper and may have additional carbon material such as sawdust it does not require waste water treatment processing as it does not contain industrial waste and other contaminants. Where the correct decomposing process is used, heat destroys pathogens which make the end product suitable for crops.
Composting Toilets: Composting toilets use little or no water and through anaerobic decomposition produce compost. The advantages are they reduce the amount of water required, they can also be used to compost other material, and they reduce the need for sewerage pipes and other infrastructure and ultimately would reduce nutrient flows into rivers and oceans. Composting toilets began in the 1960s and as more research and improved models are developed this will be a potential way forward to improve the recycling of human waste as well as reduce the amount of water required.
The future of biosolids
Biosolids presents a viable solution to the management of human waste. The future of biosolids will be strongly influenced by:
- Research and investigation to establish new and improved opportunities for uses for biosolids.
- Improvement in technology in the treatment of waste water and the production of biosolids
- Community understanding and awareness of the benefits and concerns of using biosolids, as well as understanding the environmental and waste management issues by not using biosolids and other by products.