BioCycle Magazine

Biocycle World


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An Information Sheet prepared by The Composting Association in the United Kingdom gives an overview of available options for managing “liquor” (leachate) produced at composting sites - especially following the excessively rainy spring/summer of 2007.

“Compost leachate” can be described as water that has changed in terms of its chemical properties as a result of percolating through composting or composted materials. It can be produced from moisture released from input materials and/or by rain or other water that has seeped through the composting pile.

Leachate can be distinguished from runoff, which is water that has fallen onto the pile but has not percolated through it or that has fallen onto the site surface, or a building, without touching the composting materials. While leachate usually contains a high concentration of dissolved substances and suspended solids, runoff contains lower concentrations of potential pollutants.

Liquor is a mixture of leachate and runoff. In an open air turned windrow system, leachate and runoff are likely to flow together and so cannot be separated.

The Composting Association and the University of Coventry carried out a small-scale laboratory study to investigate the potential for composting of green wastes and screened mature compost at different ages to generate leachate.

In an actively composting mass, there are large changes in nutrient cycling as complex organic compounds are broken down and stable humic substances are formed. Many water-soluble compounds that are intermediaries of the various degradative pathways may be carried away from the composting material in leachate.

A common solution for composting facilities is to take the liquor by road vehicle in a tanker to an appropriate sewage treatment plant. However, haulage costs make tankerage a costly option for most sites in anything other than lowest volumes, or as a short-term solution. The cost of tankering is affected by transport distance, the characteristics of the liquor and the amount that must be treated. This is very variable for each specific site.

Recent research at Cranfield University in the UK has looked at the feasibility and potential benefits of on-site biological treatment of compost liquor. The research was aimed at developing a low-cost, low-tech biofilter system that would be sustainable at a typical green waste composting facility. The biofilter system utilizes the biological film which forms on the surface of the filter media to transform important pollutants such as biodegradable organics and ammonia into less hazardous substances, in the presence of air.

Instead of rock chips or bespoke plastics used in conventional aerobic biofilters, some trials were carried out by using oversize material from the composting process, finished compost and granite chips. The experimental biofilters were set up inside 240 litre “wheelie bins”. Biofilter performance was compared over a ten month period.

The oversize medium biofilter performed much better than the other two filter media (compost and granite), particularly in terms of ammonia and BOD. A high quality treated effluent with a percentage of ammonia < 10 mg/l was produced on 95 percent of sampling occasions by filtering the liquor through the oversize filter medium. BOD removal efficiencies of 68-92 percent were also obtained in the oversize medium trials.

Long-term experiments reported in Agricultural Research (July 2007) show that organic farming can build even more soil organic matter than no-till farming practices. The study indicates that organic matter added by manure and cover crops more than offsets any losses due to tillage to control weeds. “This is one of a few long-term studies comparing organic farming with no-till,” reports John Teasdale, lead scientist with the USDA-ARS Sustainable Agricultural Lab in Beltsville, Maryland about the 9-year study.

Ralph Jurgens was an Animal Husbandry major in college, who loved the land and wanted to make it better by among other things making best use of compost. He was an owner of New Era Farm Service in California. He died in September after a year-long battle with cancer. As he wrote in BioCycle in his articles (i.e., “30-Plus Years of Composting Experience,” “Applying Compost in Mainstream Agriculture”), today “we are manufacturing between 80,000 and 100,000 tons of compost annually - applying mostly on central California conventional and organic farms, but also retailing compost all over the state. Within a 60-mile radius of our offices, there are 1,000 dairies -generating more than four million tons of manure each year. We work with close to 400 growers who farm well over 1,000,000 acres. The organic matter in compost is a food source for the organisms we're trying to promote.”

As reported in Scrap Tire News, European tire recycling and recovery rates for end of life (ELT) tires are on the rise, confirming the growing demand for tire derived products and encouraging further development. The positive trend in Europe was confirmed last year with more than 87 percent of postconsumer tires diverted to markets. This was a three percent rise in the recovery rate compared to 2005, indicating that the Directive has been a major driver for change, reports the European Tire and Rubber Manufacturers Association (ETRMA). The Directive places a ban on landfilling whole and shredded used tires.

In 2006, more than 3.2 million tons of used tires were generated. In 2005-2006, more than one million tons of postconsumer tires were consumed in material recycling activities including construction applications, environmental rehabilitation projects, and consumer and industrial products manufacturing. “This represents a 23 percent increase over a decade - a sure signal that the slowly maturing market for end of life-derived products is sustainable and economically viable,” sums up the ETRMA.

Producing bio-oil from sewage sludge is a promising way to improve economic value and also to reduce pollutants with sludge, according to a study by Y. Kim and W. Parker reported in a 2007 issue of Bioresource Technology. The objective was to evaluate production of oil from primary, waste activated and digested sludges. The pyrolysis was performed in a laboratory-scale horizontal batch reactor. The operating temperatures ranged from 250°C to 500°C, while a gas phase residence time of 20 minutes was maintained with 50 ml/min of nitrogen gas. The maximum oil yield was achieved with primary sludge at 500°C. Temperature and volatile solids were the most important factors affecting the yield of oil and char, however, sludge type also affected both results. Pretreatment of sludge with either acids, a base or a catalyst (zeolite) did not improve the quantity of oil produced.

The latest issue of Aluminum Now has a special section on “Recycled Aluminum Products” with these details: Recycling aluminum requires 95 percent less energy than producing aluminum from bauxite; Recycling steel requires 60 percent less energy than producing steel from iron ore; Recycling paper requires 40 percent less energy than producing paper from lumber. Because recycling aluminum requires much less energy, produces less emissions and saves money, the aluminum industry encourages recycling of all postconsumer aluminum.

From Brazil comes a line of aluminum handbags made from 100 percent postconsumer recycled aluminum pull tabs. Escama Handbags - a U.S. company - has imported bags designed by crocheting 700 aluminum pull tabs; tabs are purchased in bulk and made by artists at two craft cooperatives; artists are earning between seven and 15 times Brazil's national minimum wage.

Created by Cornell University professor Jack Elliott, the ceiling mount and base holder of the “swarf” lamp are made from recycled aluminum bar stock, while the diffuser is recycled from the swarf created by cutting the mount and base holder. The proponents are looking for a North American-based manufacturer to produce the lamp commercially.
Other products are the Emcee 20-06 Chair constructed of 80 percent recycled aluminum that weighs 5.5 pounds and stackable up to 10 feet high; Eleek's countertops and tiles made of between 80 and 85 percent recycled aluminum; and Gordon Ceilings, with specialty corrugated metal.

Asks Kurt Rosentrater of the USDA in Distillers Grains Quarterly: How much DDGS will the U.S. produce and how much can be consumed by livestock and the fuel ethanol industry? Pelleted feed reduces feed waste and dust generation and produces increased nutrient density. Disadvantages include increased space requirements for equipment, need for a steam source, and increased electricity consumption. Benefits are improved weight gains and feed conversion in livestock, plus improved feed handling and storage. “Feed pelleting is more often an art as opposed to a science, and it is common to see pellets with durability values between 25 percent and 90 percent,” says Rosentrater. “Cost to produce pelleted feeds is often between $1 and $9 per ton. Moisture is needed for feed conditioning with steam addition being sufficient. Targeted moisture content at conditioner discharge is between 15 percent and 17 percent. Too much moisture will plug the pellet mill.”

Ingredients themselves are as important as the conditioning. Feed ingredients with high starch, protein or fiber tend to pelletize fairly easily. Products with high fat or sugar contents are more difficult. To answer the question about pelleting DDGS, “my answer is yes,” writes Rosentrater. “One will probably need to use somewhat different processing conditions for each source. … There is a need to examine pelletability of various sources of DDGS from different ethanol plants; and to examine whether pelleting hot vs. cold DDGS at a feed mill has an effect. Also, more work needs to be pursued to examine whether nutrient damage actually occurs during pelleting, and if so, at what processing conditions.”

In the July, 2007 issue of BioCycle, an article on a biosolids composting project incorrectly identified the brand of a piece of equipment. “Agitated Bay Composting In Ardmore, Oklahoma” (page 50) explained that dewatered biosolids are mixed with ground yard waste then loaded into bays at the in-vessel composting facility. Ardmore uses a Roto-Mix 2300 stationary compost mixer with a 16-foot stand-alone conveyor.

An August Regional Roundup item on the Cornell Waste Management Institute's workshop series on how to compost road killed animals had an incorrect URL where readers can get more details on workshop content and dates. The correct URL is: http:// There was a workshop in July, and two in early September. Two remaining workshops are October 11 in Highland, New York and November 13 in Syracuse.

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