One of the biggest challenges that the timber industry faces is the management of wood waste that results from various production processes

The industry generates significant amounts of wood waste that is more often than not, sent to a landfill for disposal: a process that costs a lot in transport and disposal fees. Mountains of wood waste can be seen around the outskirts of Dubai and the other Emirates.

A possible solution to this problem is to treat wood waste as a resource, rather than as a problem. This can be achieved by recycling and re-utilization of wood waste as compost.

Composting is an aerobic biological decomposition process that converts biodegradable solid organic matter, such as wood, into a stable humus material at elevated temperatures (40 - 60° C). Composting wood waste reduces the waste volume, detoxifies the waste and transforms the waste into a product that can be used as a soil amendment. Composting also increases the organic matter content and improves the water-holding capacity and the texture of the soil.

The material that results from the process of composting can be, for example, used as a fertilizer that, among other things, can improve the characteristics of soil (porosity, ability to retain water, etc.) and can act as an agent for prevention of land degradation.

Studies all over the world have demonstrated that furniture scraps and waste, plywood waste, and hardwood or sawmill residue can be successfully composted. A composting operation can be implemented at a plant site and requires limited knowledge, equipment, and space.

MICO, a company based in Hohenbrunn near Munich, Germany, has developed a new production process of compost extraction with which it was possible to produce a liquid compost, which is more concentrated and aerobic and can be stored longer, and therefore gives the user more flexibility. Liquid Compost produced by the patented MICO System guarantees high quality standards.

We spoke with Georg Boehm, a representative of MICO, who told us more about the need for and benefits of composting wood waste:

Q: Why is wood waste or timber a problem in the UAE and neighboring regions more so than in the West?

A: In America, Asia and Europe, the disposal of matured or construction timber is dealt with by incineration. Construction timber ends up mostly in huge incineration plants that produce electricity and district heating. Untreated matured timber and industrial wood waste are chaffed for use as wood chips or briquettes in private homes and business enterprises for heating reasons. Both these acts are - in times where we are attempting to reduce CO2 emissions worldwide - questionable.

Then there are countries with huge natural energy sources, which have no need to use matured or construction timber for energy production. The question arises here that if this timber is not utilized for energy production, then how else would it be disposed of?

Q: What is the problem that was observed in the UAE in regards to wood waste?

A: Huge mountains of construction timber exist in the deserts of the UAE. These are the consequence of the great construction boom witnessed by the country in the last decade or so. With no need or inclination to utilize this timber for energy production via incineration, these mountains just keep getting bigger. In 2011, this observation led a German company that produces chaff cutters, to contact MICO Ltd. in Germany with the query whether chaffed construction timber can be composted using MICO-Eluate (liquid compost). MICO started tests by using MICO Compost-Eluate for composting construction timber and untreated industrial wood waste in close cooperation with the University of Hohenheim-Stuttgart, Germany. Natural wood, chipboards, and other wood products were used for these tests.

Q: What is the benefit of compost?

A: Compost - with its storage capacity of water and with its ability to change the minerals makeup of the ground - is an almost indispensable natural resource and conditioner. Composting of chaffed timber by mixing with horse or camel manure and lawn cuttings raises the carbon-nitrogen ratio, making the speed of the normal decomposition process much longer (up to 6 months). The composting of matured timber by using MICO Compost-Eluate shortens the decomposition process substantially.

Q: How did you proceed with the composting?

A: The timber was chaffed first, then sprinkled with MICO compost-Eluate and then finally, mixed with horse manure and lawn cuttings. A compound of 70 percent chaffs, 20 percent lawn cuttings, and 10 percent horse manure yielded the most optimal, useful and economic results. With very dry wood it proved beneficial to soak the chaffed pieces in an immersion bath of MICO Eluate before mixing with the other components. Per kilogram, chaffed wood can soak up 1 liter Eluate watered down to a ratio of 1:10. Chipboard can soak more than natural wood.

The high concentration of micro-organisms in the eluate results in an immediate start of the decomposition process. During the regular turning of the heaps (one or two times a week), which is necessary for mixing the outside layer of the heap with the already more decomposed material inside and bringing oxygen into the heap, the heaps were sprayed by eluate more times.

Q: How long does the whole process take?

A: In just 8 weeks a high quality of compost can be achieved. After 12 weeks, you get the optimum quality. The decomposition process can be advanced (6 to 8 weeks) if the chaffed timber is frayed additionally to give the micro-organisms more surface area to work.

Q: How did you deal with chemically coated wood?

A: A special additive proved successful especially with treated wood, which not only encourages the decomposition of hydrocarbon compounds of the wood protection agents, but also helps to decompose high-molecular ingredients (lignin, cellulose and secondary ingredients) relatively faster. This additive is a special mix of nutrients for the micro-organisms, which are able to decompose these high-molecular hydrocarbon compounds.

Q: How can the resulting compost be used?

A: The compost from treated wood could be used optimally and safely in landscaping, gardening, farming, nurseries, sports fields and golf courses etc. Since the compost from untreated timber contains no debris at all, it can be used in the food sector without any problems. However, the compost from treated construction timber contains minor traces of chemical, therefore it is not recommended for use in the food sector without laboratory tests to attest that no harmful contents exist in the compost.

© Timber Design & Technology 2013