   What is Compostable? - March 12, 2014 Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County A gardener can never have too much compost. Over the years, I’ve written extensively about composting and these “how to” articles from the past are posted to the Backyard Gardener website (see URL below). In this column, I’d like to discuss some of the lesser known raw/recycled materials that can be used in making compost. Once you understand the relative amounts of green (nitrogen-supplying) and brown (carbon-supplying) raw materials needed to make compost, you realize we do not always have necessary amounts of these materials available. Sometimes, it becomes necessary to procure these raw materials from outside sources. Manure, a “green” material, is readily available to us. Horse, alpaca, llama, sheep, goat, rabbit, and cattle manures are available to us through both formal and informal channels. Craig’s List (www.craigslist.org), an on-line service where people advertise anything they would like to buy or sell, has several manure listings in our area. Horse manure is the most plentiful and is often free for the taking. The main caution is to beware of bermudagrass (and other weed) seeds – horse manure can contain viable seed. Other types of manure are less likely to contain weed seeds, but you can ask the owner what they feed and/or graze upon. Shredded paper, a “brown” material, can include newspaper, office paper, phonebooks, and other sources. Over the years, there have been concerns about toxicity from heavy metals coming from colored inks. Evidence shows such low concentration of heavy metals - if any at all - that colored paper may be used without significant risk. Many inks currently used are soy-based. According to one science-based source, shredded computer or other office paper and glossy magazine-style paper decomposes slowly and may contain dioxins. There are enough concerns about the dioxin in bleached and glossy paper that it would be wise not to use them in the garden. I have used shredded office paper (no glossy paper) as bedding for my chickens. Once soiled, I compost the shredded paper/manure mixture. I am in the process of reassessing this practice. Coffee grounds from espresso bars and restaurants are collected and composted by many gardeners. Coffee grounds are in between “brown” and “green” having some nitrogen, but other properties and compounds that may inhibit decomposition. Contrary to popular opinion, coffee grounds do not appreciably acidify the soil. However, having greater than 20% coffee ground content in a compost pile is not recommended. All things in moderation… Brewing and wine making waste products can be composted. Wine making waste is called “pomace” and contains seeds, stems, skins, and pulp. Brewing waste contain crushed grain and hulls. These materials are still relatively high in nitrogen and should be added to brown materials prior to composting. The idea is to prevent aerobic conditions from developing. If it does, you will smell ammonia or other foul odors. Green weeds, another “green” material, can be composted as long as the flowers have not matured and produced viable seed. Grass clippings are very difficult to compost because they tend to create mucky layers that prevent aeration of the compost pile. A better solution is to mow using a composting mower that spreads the clippings evenly on the soil surface where microbes can recycle their nutrient – this also reduces fertilizer demand. As a reminder, it is still not recommended to compost meat, bones, animal/vegetable fats or oils, manures from animals that eat meat, and other materials that could attract vermin. However, it is worth mentioning that many meat production facilities are composting dead poultry, pigs, and cattle using very specific methods and controls – do not try this at home. Some gardeners use commercially available compost "starters" or accelerators. These are supposed to help the decomposition process by adding nitrogen, enzymes, and bacteria to a pile. These products are largely unnecessary as these compounds and organisms are already present. Tests conducted at universities and private research stations have showed that the best compost additives are either your own, unpasteurized but finished compost or native topsoil from your garden. Composting is not difficult and becomes routine once you learn what resources you have, what’s missing, and where to procure the missing materials. Follow the Backyard Gardener on Twitter – use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8999 Ext. 3 or e-mail us at verdevalleymg@gmail.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.  |