This paper describes how the Cambi Thermal Hydrolysis Process (THP) treats biodegradable organic waste and converts it to renewable energy and pathogen-free and bio-fertilizer. The interest for the process is expected to increase due to new environmental legislation as well as increasing demand for renewable energy. The implementation of the European Landfill Directive 1999/31EC and the Animal-by Products Regulation (ABPR, 1774/2002/EC) are two major regulatory drivers in the European Union. This paper should encourage and will assist energy companies, waste management companies and consultants to carry out comprehensive feasibility studies prior to investment, including technological, economic and environmental aspects. Due to increased environmental awareness there is a growing interest for biological treatment of renewable sources and organic waste. Increasing environmental pressures on waste disposal (landfills) have also increased the use of anaerobic digestion (AD) as a process for reducing waste volumes and generating useful byproducts. An anaerobic digester is an industrial biological system that harnesses a natural process to treat and convert biodegradable organic waste, producing digestate and biogas. The digestate can be converted to organic fertilizer by a short maturation/composting. The biogas can be used to:
- provide heat
- power a gas engine to produce electricity and heat
- produce compressed bio-methane after CO2 removal that can be used as vehicle fuel gas,
The Cambi thermal hydrolysis process (THP) is a well proven and patented technology to pretreat biological waste for sterilization and high organic matter conversion. Organic waste treated with thermal hydrolysis at high temperature undergoes both extreme disintegration, i.e. breaking up cells and dissolving organic solids into water, and complete pathogen, seed and helminth (parasite) kill. In the THP process complex carbohydrate and protein substrates are reduced to single monomers of saccharides and amino acids that rapidly acidify in the digestion process to give short chain volatile fatty acids. These fatty acids are rapidly converted to biogas in an anaerobic digester. The positive consequence is increased and accelerated biogas production during anaerobic digestion and improved dewaterability of the digested product (digestate).
In a conventional digester a complex range of micro-organisms slowly undertake the process of biological hydrolysis that limits the rate of biogas production. In the Cambi process hydrolysis occurs rapidly as a result of heating the material under pressure to around 165°C and then releasing the pressure. This results in substantially more of the biodegradable material being made available for conversion into gas. All inputs to the digester are sterilized and therefore there is no risk of pathogen contamination in the digestate. The technology was first implemented in Norway at Hamar in 1995 on sewage sludge and subsequently applied to biodegradable municipal waste (BMW) at a plant nearby Lillehammer. The organic waste is treated at a minimum of 133°C for 20-30 minutes combined with pressure drop disintegration prior to anaerobic digestion. ABP Regulations for cat II material require a temperature treatment of min 133°C for 20 min. The plant is currently treating source separated household waste and ABPR category III waste. The customer is considering upgrading the plant to treat category II waste.. With a new separate reception hall combined with the high temperature treatment the plant will meet the Animal-by Products Regulation (ABPR, 1774/2002/EC) treatment method 1 which allows treatment for cat II waste as well. Conventional pasteurization systems use 70°C for 60 minutes and cannot treat ABPR cat II.
It is very important that new AD facilities fulfill the Animal By-Products Regulation (ABPR EC 1774/2002). Several biodegradable organic waste fractions can be classified as ABPR cat II and III material. Due to the high-temperature thermal hydrolysis process the Cambi system is adapted to these more stringent environmental requirements. Environmental requirements for organic waste treatment have always grown stricter and there have so far been no signs that this process will stop.