THE dump truck pulls up at one end of a long, greenhouse-type structure on the outskirts of this rural community and offloads its cargo: several days' accumulation of apple pomace from a cider and juicemaking mill. The scene is repeated all week long with a variety of other wastes, principally manure from local dairy and chicken operations and more distant horse-racing stables. What starts out as a sloppy, odoriferous mess at one end of the building emerges 18 days later from the other end as a dry, peatlike, odor-free and profit-making material, To the uninitiated, the transformation appears almost miraculous.
Simple and relatively inexpensive composting technology, developed in Japan and modified in the United States, enables the Earthgro Company to convert potentially polluting wastes into sought-after products, sold through garden outlets around the country. Most significantly, the transformation is taking place on a smaller scale and at much lower cost than was previously deemed possible. Moreover, the Japanese operations have shown that sewage waste can be composted as well.
Says Dr. Geoff Kuter, head of research at the Connecticut facility: ``We're producing 20 tons of dry compost every day, and we can't make enough to meet demand.''
The eight-month-old plant is the latest to benefit from the increased understanding of large-scale composting coming out of universities and agricultural colleges in recent years. In contrast to the general rule where progress often is accompanied by ever more complicated technology, this new knowledge has simplified the engineering needed to compost solid waste effectively.
Little more than a decade ago, long-held prejudices against composting were still widespread in the US, and the professor who openly stated his desire to specialize in solid-waste composting might have jeopardized his academic career. But today all that has changed: Composting is now both a respected and a practical science. It is also being slowly recognized worldwide as the most acceptable and cost-effective way for a world with 5 billion inhabitants (twice as many as 35 years ago) to handle its organic wastes, according to Henry Hoitink, a plant pathologist at Ohio State University and a leading expert in compost science.
Dr. Hoitink, one of a handful of biologists in this country to investigate biological waste reduction even before it was deemed respectable, contends that the global trend in this direction is irreversible.
``We are learning that we can no longer walk away from this problem. The environment,'' he warns, ``simply cannot continue to accept the volumes of unprocessed organic waste we are producing.'' The alternatives, landfill and incineration, present problems of their own, including lack of space and soil (for landfill) and costs that are rapidly outdistancing those of composting. Composting, Dr. Hoitink points out, reduces the volume of waste at least by half and leaves it in a highly stable form so that runoff from composted farmlands presents no threat to rivers or underground water supplies.
The improved understanding of what occurs during the breakdown of large compost heaps opened the way for the less costly engineering that characterizes the Lebanon, Conn., operation and some others such as the Paygro compost plant at Charleston, Ohio. Where it was long assumed that rapid decomposition was equated with high temperatures, it has been discovered that optimum breakdown occurs at 55 degrees C. (131 degrees F.), which is high enough to destroy all harmful pathogens. On the other hand, too high a temperature slows decomposition by killing most of the beneficial microorganisms.
By the simple technique of forcing air through the composting pile, two things are accomplished: Temperature is checked by evaporative cooling, and the improved oxygen supply discourages the growth of anaerobic, stench-producing bacteria. Turning the compost regularly (as every backyard gardener knows) is another way to introduce needed oxygen.
Forced air and mechanical turning, both involving straightforward engineering, are principal features of the Earthgro and Paygro systems and a few others in the US, but the Japanese-developed Earthgro system is the simplest and, so far, least expensive of all.
Dr. Andy Higgins, a Rutgers University composting expert, toured Japan specifically to investigate their composting plants. What he found were very effective operations that could be readily sized to meet any need, small or large. On his recommendation, the Earthgro company adopted the Japanese system. ``The only drawback to the system,'' he told Dr. Kuter, ``is its cost. It's too cheap for most Americans to take seriously.''
The Earthgro plant involves four parallel concrete troughs (6 feet, 6 inches wide, 6 feet deep, and 180 feet long). Once a day, an automated machine travels down each trough, turning the compost and moving it back 10 feet. A batch of raw waste (mixed with sawdust to absorb excess moisture and balance the carbon-nitrogen ratio needed for good decomposition) takes 18 days to travel the 180 feet before it emerges as the finished product.
Beginning soon, a dozen smaller communities in the region will bring sewage sludge for composting on a trial basis. At first, sawdust will be added to provide the needed bulk, but later the towns' solid waste (with non-biodegradables removed) might replace the sawdust. (Composted sewage is not the same as Milorganite, a product that has long been on the market. Milorganite and other similar products are dewatered and cooked dry, rather than composted.)
Where composted farm and food wastes could be spread on any agricultural lands or private gardens, Kuter believes that for the forseeable future composted sewage would be confined to ornamentals, lawns, playing fields, and the like because of possible contamination by heavy metals from industrial waste.
Kuter estimates that a similar system processing 40 wet tons a day could be installed and ready to run for ``about a million dollars.'' That's about a quarter the cost of most comparable facilities, ``the result of simplifying the system,'' Kuter says. ``You have to hand it to the Japanese.''