SINCE July last year, the municipalgarbage dump at Gladokvarn, outsideStockholm, has been yielding gas at therate of 22,000 in per day from gas wellsup to 20 in deep. The gas is carried via a13 km-long pipeline to a 5 mw heatingplant which, in turn, supplies centralheating to the nearby Skogas housingestate - enough to heat some 2,500single-family houses.
It is a well known fact that household garbage, compacted over long periods of time, creates large quantities ofmethane gas. Many attempts have beenmade in the past to bring the gas to thesurface and harness it, not just forcommercial purposes but also toprevent it from leaking into theatmosphere and contributing to thegreenhouse effect.
The technical problems involved,however, have been difficult to solve.The main problem is to be able to drilllarge and deep well holes through layerupon layer of material containing such awide variety of waste. However, engineers in Sweden claim to have foundalmost a complete answer.
The drilling at Gladokvarn was carried out by Svenska Borr AB, using anAtlas Cop Geodrill 800E equipped with asix-inch-hollow stem auger, a drillingtool. The hollow stem auger is normallyused for soil investigation, groundwatermonitoring and well-drilling. The augerhas no trouble with small metal objectsand simply pushes larger objects aside.Wood, concrete and stone can givesome problem by slowing the rotationdown, but generally speaking, it drillsright through without stopping.
During the first two weeks ofdrilling through the compacted household waste consisting of every conceivable type of material, eight holes varyingfrom 15 in to 20 in deep were drilled.The engineers soon learned to operatethe wireline system. The deepest holedrilled was 22 in deep and was completed in less than 24 hours. Now almost70 holes have been drilled, of whichabout 50 are active.
The company claims that it is thefirst in Sweden and probably one of thefirst in Europe to use a hollowstem auger for this type of work,which although not problem-free, isvastly superior to conventional drillingin these circumstances.