Solving the Garbage Glut—With Compost
BY AWAKE! CORRESPONDENT IN FINLAND
AS MANKIND’S garbage piles up, it poses one of the toughest dilemmas of our age. Modern technology, adept though it is at producing garbage, seems quite at a loss when it comes to getting rid of it. The obvious, time-honored solutions are fraught with problems. Since dumping the garbage may pollute neighboring groundwater, many countries have forced garbage dumps to close. And burning the garbage can release toxic chemicals and leave behind ash, both of which present their own disposal problems. High-technology incinerators are thus unpopular in many areas.
What alternative is left? Some suggest a natural way of getting rid of solid waste—a sort of biological “fire” called composting. Like fire, composting reduces organic matter into a number of by-products, releasing heat in the process. The by-products of composting can be quite useful. The gases and heat may be used as sources of energy. And the solid by-product, humus, is a valuable soil fertilizer in agriculture.
Composting is growing in popularity. In Finland, for example, the town of Korsholm and its neighboring city Vaasa have developed an advanced garbage processing plant that uses composting. The plant’s designers found an ingenious way to solve two of the region’s problems at once. Gravel for construction and roads is a scarce resource. Hence, the idea to blast a wide, 130-foot [40 m]-deep hole in the bedrock. After producing great amounts of gravel, the hole formed an ideal site for a huge bioreactor to treat municipal waste. Being surrounded by solid rock helps the reactor to maintain the constant temperature so essential to the fermentation process.
The result? To a large extent, this modern plant has solved the region’s garbage problem. It reduces garbage in volume by 75 percent and in weight by 66 percent. How is this possible? Let us visit the plant.
A Unique Garbage Treatment Plant
Our first impression on arriving is that this place has little in common with conventional garbage dumps. There are no rats, and there is no foul odor. Here waste management seems only another productive industry.
The plant manager first shows us a chart explaining what happens in the plant. A two-step process reduces most of the bulk and volume of the garbage—first composting it and then rotting it. In composting, the waste is broken down in the presence of air; in rotting, it ferments without exposure to air. But before either of these processes begins, the waste is crushed.
From a window of the control booth, we see a garbage truck backing through a big door. It dumps the garbage into a huge funnel-shaped pit, where a belt feeds it into a shredder. Larger objects, such as bicycle frames, car tires, exhaust pipes, and most pieces of plastic, are removed by a crane. Our host explains that when old refrigerators and freezers come in, they are sent for repairs and are later sold to less-developed countries.
After the first crushing, the waste goes through a coarse sieve where everything smaller than two inches [50 mm] falls through. This is about half the garbage, and it passes on to the first step of its biological treatment, the composting. This takes place in a large tank where the crushed waste is mixed with sludge from the city’s sewage treatment plant.
“When developing this process, we were always thinking of the environment,” says our host, “therefore, we even separate the dust that comes from the crushing. Furthermore, we blow air into the composter tank where the mixture of waste and sludge is homogenized and heated to approximately 40 degrees Celsius [104 degrees Fahrenheit]. The air coming out would stink terribly because of aerobic decay if we did not pass it through a filter first.”
After one or two days in the composter, the material enters the main 130-foot [40 m]-high biogas reactor. What happens here? Well, the organic components of this mixture are decomposed by tiny microbes that can live in this oxygen-free environment. This stage of the process is called, simply enough, rotting. It takes 15 days at 95 degrees Fahrenheit [35° C.]. The final products are biogas and humus mass, which is about 85 to 90 percent water. Most of this water is pressed off and fed back into the reactor.
But what happened to the half of the garbage that never got through the sieve? Our guide says that this part is quite combustible because it consists mainly of paper and plastics. But to burn the waste safely would require a temperature of over 1,800 degrees Fahrenheit [1,000° C.]—and there is no such incinerator in the neighborhood. “That is why we crush the remaining waste once more and feed it back into the process,” he says. “It is true that the biological process is unable to break down plastics, but the waste is mostly paper, which finally becomes humus compound.”
What does this complicated process produce? Our host answers: “Mainly we get two products, humus compound and biogas. We sell the humus mass for building up green areas and covering closed landfills. There is a great need for this now that many old dumps are closed. For the future we have to see whether it can be used in agriculture after removing glass and plastics. The biogas consists of 60 percent methane and 40 percent carbon dioxide. In quality it corresponds to natural gas and is used in the same way. We have a pipeline system for distributing it to the closest industrial plants.”
What about problems with heavy metals in garbage and sludge? Our host continues: “These heavy metals are concentrated in the water. Therefore, we intend, in the future, to acquire equipment for removing heavy metals from the water. Then our product may be good for all purposes. When we talk about the future, I must tell you about my dream, which is that all households would sort their garbage so we would receive neither glass, plastics, nor metal. All of that is recyclable. Even synthetic textiles, plastics, and rubber are recyclable.”
The plant has the capacity to deal with the waste produced by 100,000 people. This is important in Finland. By the year 2000, this country plans to put about half its garbage to use—in the form of either raw materials or energy.
Our tour has given us concrete proof that it is possible to do something about the garbage glut. Each of us can cooperate with whatever recycling laws are in effect where we live. Before we leave our guide, though, we ask if there are many plants treating garbage as effectively as this one does. “That is difficult to say,” our guide answers. “I do not know of any similar plants. Maybe the problems are so much bigger in many places that nobody has dared to try this.”