Proceedings

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.

Key words: Thermal hydrolysis, biowaste, pre-treatment, anaerobic digestion, biogas, animal
by-products.