ENK6- 2002-30030 ENERDEC - Maximum energy yield from organic wastes and decontamination to a high quality organic fertiliser by a microbiological hybrid process

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Biological Conversion : Composts/Fertilisers : Crops for Composts/Fertilisers : EESD (Energy, Environment and Sustainable Development)

Proposal No:	ENK6- 2002-30030
Date Prepared:	February 2004
Source:	European Bio-Energy Projects (EUR 20808)

Introduction

The project's approach is based on the state of the art of the following disciplines: organic waste composting and digestion, biogas up-cleaning, reduction of organic waste contaminants, and environmental contamination through liquid manure fertilising. Energy production from organic wastes, based on biological methods, can only be achieved by generation of biogas via the digestion process. We want to achieve maximum energy yield from the digestion process by means of an innovative digestion technology and optimised process control of wastes from slaughterhouses and the leather industry.

Fuel cells (FC) have been developed mainly with natural gas as the fuel. The introduction of biogas into the natural gas grid requires the removal of inert components in order to improve energy density and to meet existing standards. The main parameters that may require removal in an upgrading system are H₂, water, CO₂ and halogenated and silicon containing compounds. Closing the gap between 50 ppm (state of the art) and 10 ppm H₂S (required by the FC) will be achieved by an especially reliable biotrickling filter, as well as technologies to remove siloxanes, CO₂, and C_x, H_y, compounds.

Today, reduction of organic waste contaminants can only be achieved either by mixing the material with non-contaminated additives (e.g. wood), or by the addition of complexing agents and separation of the soluble metal complexes.

The Komptech-Farwick`s B.S.F.C. process (Biowaste Separation Fermentation Composting) is able to reduce heavy metals and salt contamination in organic wastes exclusively by dry mass splitting to produce an up-cleaned compost without dilution methods. The aim is to optimise depletion of heavy metals and salt in the raw material for composting by improving the separation process performed through a mash-separator. Furthermore, an economically acceptable method to reduce N and P contamination in the liquid digested residues has to be developed. The new technology will smooth the way for the construction of small, autonomous plants which are highly adapted to local situations.

Progress

After half a year, work on the project is progressing according to schedule. In the digestion part of the project, different types of organic wastes, such as kitchen waste, slaughterhouse waste and pulper waste, were pre-processed under different conditions and tested for their digestion behaviour, their potential for biogas formation, and the composition of liquid digested residues. The slaughterhouse wastes were investigated in more detail: After separation into five fractions, each was processed in continuous lab-scale digestion units as a basis for specific loading calculations.

For the methodological development of a purification treatment for the digested residues, two different reactor types - a sequencing batch reactor (SBR) and a fluidised bed reactor (FBR) - were installed at laboratory scale and operated using centrifuged digested residue to maintain the process parameters. Nitrification was observed to be quite good, as was denitrification, but the latter process depends on the availability of carbon which might be insufficient. Currently, tests are running with the addition of an external carbon source. COD could be degraded from an initial 10 g/l to concentrations below 1 g/l.

Centrifugation experiments on digested residues on a technical scale provided the necessary amount of digested liquid for these investigations. Arrangements for experiments on the reduction of heavy metals and salt content in the solid products of the B.S.F.C. process have now been finalised - a survey of the process was performed by detailed monitoring of the method.

A suitable filter arrangement was planned for the biogas upgrading tasks. As a first step, a laboratory-scale biotrickling filter is actually being constructed in order to optimise H₂S removal. The lab tests started in July and will run until December. Based on the results, a prototype will be constructed and combined with membrane and activated carbon technology for the removal of the detrimental compounds. This prototype system will be tested under field conditions in Spain in March 2004. It is assumed that in 2004 a second organic waste treatment plant at industrial scale will be available near Vienna for on-site investigations.

Impact and exploitation

ENERDEC will help to create a set of technologies for use in the fields of renewable energy, biotechnology, agro-industry and environmental protection. These technologies will help to strengthen the competitiveness of the SMEs involved by expanding their competence and experience in the waste-treatment and energyproduction sectors, as well as contributing to the sustainable care of the environment by recycling waste into the product cycle.

As a technological impact, the digestion process will be combined with the improved composting technology to establish a new B.S.F.C. technology of solid organic waste treatment systems on the market and to restructure existing plants. A concept for decontamination of liquid digested residues, which must be both economically and ecologically attractive, will raise the acceptance of such technologies. Another main impact should be the application of a biological biogas purification system to pass the up-cleaned biogas into the natural gas grid.