Background The EU has a major and growing environmental problem with sewage sludge due to increasing population, the building of more treatment plants and a lack of efficient technologies for dealing with it. Implementation of the EC Directive on Urban Wastewater Treatment, with its stricter treatment requirements, has lead to a dramatic increase in the amount of sewage sludge produced throughout Europe in the past 15 years. In 2005, when this project began, nearly 9 m tonnes of dry matter was being produced each year compared to 5.5 m tonnes in 1992. Application of the sludge to agricultural land is seen as the most sustainable solution, but despite its high agronomic value, such use has been controversial because of the hazards of contamination from heavy metals and pathogens. Techniques used around Europe to treat sludge for agricultural recycling all have limitations in terms of speed and capacity, but more particularly in guaranteeing elimination of pathogens. Objectives One treatment method known as MAD – Mesophilic Anaerobic Digestion – lent its name to this project, “MAD but better”, because the beneficiary set out to demonstrate that an adaptation of the process using high rate enzyme hydrolysis is the safest and most efficient way to enhance treatment of sludge for recycling on the land. The new system is based on an entirely natural microbial cycle. It harnesses the actions of a series of bacteria to accelerate the mineralization process of complex organic matter, to return nutrients to the soil while destroying pathogens. The resulting soil conditioner or fertilizer was expected to exceed the strictest current and predicted European safety standards, as well as being faster to produce. Methane given off as a by-product of the method was to provide all the power needs of the system, plus more for onward supply to the grid. A final aim of the project was to disseminate results throughout Europe to help overcome negative perceptions of the risks associated with using sludge on the land and to promote the new system as the safest, most cost-effective and sustainable option for dealing with the ever-increasing problem of sewage sludge. Results Together with the project partner, the beneficiary established an installation of the MAD process at one of their wastewater treatment plants in north-west England. It was the first demonstration of this innovative technology at full capacity and results met or exceeded all specific objectives except energy recovery - attributed to constituents of the feed. The process delivered a pathogen kill capacity of 99.9999%, a figure so high that the main problem was accurately monitoring such a rate. Because secondary digesters were not required, the process time of between 10.2 and 16.8 days was two to three times faster than traditional methods. Total sludge treated was 12 511 tonnes of dry solids. Based on achieved rates and at maximum hydraulic throughput of 740m3 per day, the annualised throughput would be 14 860 tonnes of dry solids per year exceeds the target of 13 500 tonnes. Energy recovery efficiency, although slightly lower than expected, was 57 – 63% compared to the usual 30-50%. At the maximum throughput rate and 55% energy recovery efficiency, the plant still delivers 13 MWh pa of electricity. A total of 8 490 tonnes of treated sludge with high agronomic value was produced (exceeding the 6 000 tonnes target). Heavy metal content of the sludge cake was well below limits set by EC Directives. The sludge proved to be of low odour and entirely suitable for spreading on grassland, even close to residential areas. Disposal cost equated to €240 per tonne of dry solid. Use of sewage sludge typically saves €175 per hectare in fertiliser replacement for farmers. If the benefits to farmers are taken into account, the cost of sludge disposal is further reduced to just €210 per tonne of dry solid - this compares very favourably with average landfill costs of €415 per tonne. The project’s technology has now become the new sludge treatment standard for the entire UK water industry. By August 2007, four Enzymic Hydrolysis Plants had been built by the beneficiary and five ordered by other UK companies. The project also worked to demonstrate that the technology could be fitted retrospectively to existing anaerobic digestion treatment plants and interest is being shown by countries around the world. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section). This project has been awarded the title of "Best of the Best" from a shortlist of 22 "Best" LIFE Environment projects in 2008-2009.