Objective
The aim of the project is to demonstrate improved perspectives concerning energy, resources, environment and economy by utilization of composting heat plants and anaerobic fixed film reactors in integrated systems, where solid and liquid organic waste products (primarly from agriculture) form the basis for a production of compost, earthworm biomass for live fish feed, pisciculture with eel, waterhyacinth for feed and energy production, greenhouse and outdoor cultures, and where the composting heat, biogas and heat exchanging supply a large part of the energy consumed in the integrated production.
The integrated plant has proved to be environmentally friendly and no major technical problems have been encountered, but the energy production in the heat composting plant was less than expected, mainly due to lower feeding rate of organic matter, because of lower volume weight of the organic wastes. Composting of 550 t/year resulted in a net energy production of 6.3 TOE, which were used for heating of the water in the eel production plant.
Different organic waste mixtures were formulated and composted in the heat composting plant at about 60 deg. C in periods of 1-3 weeks, resulting in a satisfactory hygienization. The raw compost was stabilized in aerated static piles with temperature feedback control. A nutrient poor compost was produced, which could replace up to 50 volume-% of peat in horticultural substrates. The vermiculture plant was only constructed in mini-scale and the vermi-composting tests were rather unsuccessful as regards compost stabilization capacity and worm biomass production. However, feeding tests with live worms showed, that the eel preferred live earthworms to dry fish feed.
When biogasifying separated slurry, the optimal running of the 20 m3 anaerobic fixed biofilter, as concerns energy production, was 5 m3/day, and the net energy production was about 29 TOE/year. A considerable reduction of COD, total N and total P was obtained by treatment of the separated slurry in the anaerobic fixed biofilter and the water hyacinth plant. The evaporation in the water hyacinth plant was between 2-7 l/m2/day, depending on the season of the year, and at optimal conditions (July) the water hyacinth biomass production was 260 g wet weight and 17 g DM/m2/day. The protein content was about 26% of DM. When treating eel waste water, the maximum capacity of the anaerobic fixed biofilter, as concerns denitrification, was 90 m3/day. The denitrification process reduced the water consumption in the eel production plant and the waste water discharge by about 64% (from 140 m3/day to 50 m3/day). Hereby a net saving of energy of about 14 TOE/year was obtained. Running of the water hyacinth plant was not economically feasible due to high investments and running costs, because of the long, dark and cold winters in Denmark.
Financially the project was not a success, mainly due to problems concerning obtaining long time financing. However, the single units and various integrated combinations of the units may be or become economically feasible, as the environmental regulations are becoming more and more strict, e.g. composting of source separated household waste in the heat composting plant, which has been tested with promising results after the project was terminated, the slurry/waste water treatment line in warmer climates and the eel/fish production plant combined with the anaerobic fixed biofilter for denitrification of the waste water.
The plant consists of a solid waste treatment line and after project nr BM/446/86/DK has been transferred in April 1989 - also of a liquid waste treatment line. In the solid waste treatment line the composting heat plant is the central element in an exploitation and recycling of solid organic waste products (primarily manure but also industrial wastes and wastes produced in the system itself). The composting heat is used for heating of the integrated plant. The hygienic compost, which is formulated into compost products adapted to specific utilizations, is cured in windrows and by earthworms before it is sold or used for cultivation of plant cultures in hothouse or outdoor. The earthworms are used as live feed for the eels. In the liquid line slurry, treated by mechanical separation, is used for biogas production in an anaerobic fixed film reactor. Afterwards slurry is purified (and evaporized) in aquaculture with waterhyacinths. After the measurement period the liquid treatment line will be used for purification of waste water from the eel production plant to enhance recycling of water in the plant. Waterhyacinths will be harvested regularly and used for feed experiments or energy production by composting.
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
7500 Holstebro
Denmark