- tropical bananas, courtesy of onur mumcu.
- harvested corn field, courtesy of Ariel da Silva Parreira.
Light my Fire with Banana Briquettes
What covenants have I made to cut down on my own garden waste? My promise is: Harvest when ready and ripe. Use up everything and put everything to use.
Mahlon, my Amish neighbor, stopped by the other day in his buggy to survey my garden. The cool-weather crops were just coming on, the broccoli forming its small, tight heads, the kohlrabi stems beginning to bulge, the Black Seeded Simpson lettuce leaves flapping loose and free in the breeze.
Were eating lettuce now, Mahlon said. We eat salads for dinner, lettuce on sandwiches for supper, and even lettuce chopped up into our eggs for breakfast.
Ive learned from the Amish to eat up whats available in the garden, to preserve enough for the winter, and to sell or give away the rest. Leftovers go into the dogs bowl or into the soup pot. Any other scrap of waste goes into the compost heap, but sometimes I wonder if I could do even more with my garbage.
Scientists have been working on ways to solve environmental problems with creative uses of garbage.
One solution: Make banana peels into cooking briquettes.
British bio-energy engineer Joel Chaney at the University of Nottingham in England shredded banana peels in a meat grinder, combined the pulp with sawdust in a food mixer, compressed the concoction in a mold, and oven-dried it at a low temperature. The result: banana briquettes with the combustibility of charcoal. Light them on fire and cook your next meal.
In parts of Africa, firewood is hard to find, but banana trees are plentiful. Women who cannot afford other fuels, like natural gas, often spend four to five hours a day gathering wood for cooking and heating. Released from this daily search, the women could make constructive use of their time, and deforestation and erosion could diminish.
The Nottingham experiment makes me wonder if I couldnt make briquettes myself from my own tree waste. Every year I harvest bushels of pears from my two trees and make dried fruit. Masses of pear peelings, cores, and seeds go into the compost bin. About this same time of year I also harvest hickory nuts that fall from my tree in the pasture. I crack open the hard shells, pick out the nutmeats, and toss more waste into the bin. Hickory pear briquettes, anyone?
Environmental engineers and agricultural scientists have spent a lot of time lately trying to deal with waste, fuel, erosion and climate change, but most of their solutions appear much more complicated than the banana briquettes.
For example, in an article in Climatic Science in 2001, Gregory Benford, physics professor at the University of California-Irvine, suggested that greenhouse gas emissions could be drastically reduced if farmers dumped a large portion of their crop residue into the sea. Left in the field, corn stalks, bean and potato stems decompose after the harvest and release carbon into the atmosphere. Dropped into the oceans at depths of at least 1,500 feet, vegetable matter decomposes very slowly and could remain there in place for as long as 1,000 years.
Stuart Strand at the University of Washington read the report and estimated that sea sequestration could cut global carbon emissions by 15 percent per year. But there are problems to contemplate: What would eventually become of all those bales of waste dumped into the oceans? What would happen to the displaced water? What would become of the pesticides and herbicides the bales carry? How would we manage an underwater dumping ground? And what about the carbon footprint of bales and bales of wheat husks and corn stover (leaves and stalks left in the fields), trucked to the coasts or loaded on barges? Even factoring in transport, Stuart claims, sea sequestration could be 92 percent efficient much more efficient than the other popular solution for the climate problem posed by crop waste: cellulosic ethanol.
Scientists at the National Soil Tilth Laboratory in Ames, Iowa, are studying the amount of corn stover that can be converted into fuel. They are also studying the amount of stover that needs to remain in the ground to recycle essential soil nutrients and to prevent erosion. The researchers concluded that a normal cut harvest (leaving the field with at least 16 inches of stubble) was best. This kind of harvest would result in the most economical and efficient harvest for ethanol production.
But USDA soil scientist Ann Kennedy says that harvesting crop residues may not be the best idea for farmers especially for those cultivating fields in drier areas. Organic matter in the soil, or well-decomposed crop residue, tends to decline with cultivation. And organic matter is vital. It helps the soil hold water and contributes to the formation of clods that help prevent wind erosion. Kennedy recommends no-till (or direct-seeding) planting methods to increase organic matter in the soil.
Kennedy thinks that multiple tillage methods, those which require repeated swipes of the plow to mix residue and soil, may work too well and in the end, not increase organic matter in fields. Microbes in the soil will pig out, eat and break down the organic matter too quickly and release carbon dioxide into the air. Its best to leave crop residue on the soil, Kennedy says, and the microbes will slowly break it down and convert it into organic matter with a lot less carbon dioxide loss.
Baling up even part of crop residues would simply deplete organic matter. If residues were harvested, Kennedy says, organic matter levels would drop, and the farmers would have to find other ways to amend their soils. Without organic matter, soils become lifeless, plant roots weaken, pests become more of a problem and yields drop. Farmers and gardeners need to constantly replenish organic matter, so stripping off residues may cause more problems than its worth.
Scientists at the Rodale Institute in Kutztown, Pennsylvania take a more visionary approach to garden and agricultural waste. Last winter, Timothy LaSalle, CEO of Rodale, visited Iowa State University, where I teach, and spoke to a group of organic farmers and activists about the Institutes research on carbon sequestration. LaSalles first slide showed an experimental agricultural field that used composting, crop rotation, and cover crops to prevent the release of carbon. The field shown in the slide had been planted in hairy vetch, a common cover crop used in organic methods to replenish the nitrogen in the soil. A tractor pulled a roller through the field before spring planting, tamping down the legume and transforming it into a thick mulch that both loosened the soil and smothered weeds. Farmers then direct-seeded their crop through the mulch, eliminating the need for cultivation and herbicide use.
LaSalles second slide looked like science fiction. A microorganism with two huge eyes and a long tail filled the screen. These creatures, mycorrhizal fungi, are more prevalent and diverse in organic gardens and farms than in conventional soils dependent on synthetic chemicals. But heres the exciting news: The nodules or eyes of these fungi contain a gluey-like substance that enriches the soil by aggregating organic matter with clay and minerals. These soil aggregates are more likely to conserve carbon, holding it underground rather than releasing it into the atmosphere.
What does all the Rodale research mean? It means that the Institute has developed a method of working the land that not only does not release carbon into the air, but actually holds the chemical underground. What are the implications of this research for climate change? The Rodale Institute thinks that if their method were widely used, agriculture could become one of the most powerful strategies in the fight against global warming. The Institute estimates that if organic agriculture were practiced on the planets 3.5 billion tillable acres, we could sequester nearly 40 percent of our current CO2 emissions.
I glance out my window and watch Mahlon and my other Amish neighbors tilling their fields with their horses, practicing an age-old form of organic agriculture that has maintained and enhanced their fields for over 150 years. Their method of farming has stood up over time as one of the most environmentally sound systems. Now the environment is changing, and with its threat have come fascinating innovations in the way we feed ourselves. Scientists like Joel Chaney, Stuart Strand, and Ann Kennedy are thinking outside the box of the typical farmstead. The Rodale Institute has taken the Amish method of farming to an even higher level.
High on the branches of my pear trees, reddish green knobs are forming, bulges that will become fully formed fruits in just two months. The limbs of my pear and hickory trees bend in the swirl of a summer breeze, nodding together, beckoning me to step outside my door.