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Waste Not,Pollute Not

CRITICAL CHALLENGES 2002

BY HARRY GOLDSTEIN Senior Associate Editor

Can farmers turn waste into watts and keep our water supply clean, too?

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tick it right up to your nose,” farmer Robert Amantold me. “You’ll be pleased.”

I scooped up a handful of fluffy black compostand sniffed. It smelled slightly sweet, like richpotting soil. I never would have guessed it was

recycled cow manure if I hadn’t seen AA Dairy’sbarn and its tenants: 550 Holsteins whose digestive tracts arejust the starting point of Aman’s system for managing hisanimal waste.

In the United States, animal waste, agricultural chemicals,and eroded sediment from irrigation foul over 275 000 km ofwaterways and account for 70 percent of the nation’s water pol-lution. The situation is not unique to the States. “In virtually everycountry where agricultural fertilizers and pesticides are used,they have contaminated groundwater aquifers and surfacewaters,” according to “Solutions for a Water-Short World,” areport by the Population Information Program at the JohnsHopkins University Bloomberg School of Public Health, in Bal-timore, Md.

The choices farmers make about how they farm have a directimpact on the quality of our food and the purity of our water.Sustainable farming systems minimize the use of chemicalfertilizers and rely instead on the processing and judiciousapplication of animal manures, alongside minimal tillage andcrop rotation. Farms could even one day produce enough powerto sustain themselves as well as their rural neighbors. But cansuch approaches feed a growing world population while pre-serving the integrity of the water supply?

Cow power

In 1997, prompted by complaints from his neighbors about astrong odor of manure, Aman visited Mason Dixon Farms Inc.,in Gettysburg, Pa., looking for ideas to solve the problem.Twenty years earlier, Mason Dixon had become the first com-mercial farm in the United States to process its manure throughan anaerobic plug-flow digester. The digester is basically a longtrough with an airtight cover, which expands as anaerobic bac-teria break down waste material and release mostly methanegas. The gas powers a generator and has made Mason DixonFarms independent of other power sources.

For years, anaerobic digesters have been used to processmanure in countries like Germany, Denmark, Sweden, China,India, and Zaire. The idea is finally catching on in the States, andmay get a push as U.S. farmers grapple with the consequencesof consolidation in the livestock industry. The last 30 years haveseen more animals and more animal waste being producedwithin smaller geographic areas. In response, thousands offarms have constructed huge waste-storage lagoons, some ofwhich hold millions of liters of liquefied waste. If handledimproperly, the waste may spill into surface waters or leachinto groundwater. Neighbors often complain about noxiousodors emanating from large open-air lagoons, a stench strongenough to sting the eyes and shorten the breath.

Inspired by his visit to Mason Dixon, Aman decided toinstall a digester on his own large dairy farm in Candor, N.Y.,located about 400 km northwest of New York City. The design

engineering work was partly funded by AgSTAR, a programsponsored by the U.S. Environmental Protection Agency(EPA), in Washington, D.C. To date, AgSTAR has providedtechnical assistance to 31 digester installations on swine anddairy farms throughout the country.

The AA Dairy setup is fairly straightforward [see diagram, pp. 74–75]. In their barn, the Holsteins eat from a trough andeliminate on the floor, between trips to the milking parlor.Manure and urine are scraped into a receptacle and flow downinto a holding tank. Periodically, a pump feeds a batch of thewaste into the digester, a receptacle about 9 meters wide by41.5 meters long and 4.25 meters deep, with an airtight cover thatswells as gas is produced. Each new plug of waste pushes mate-rial further through the digester, where anaerobic bacteria feaston the sludge, releasing on average 1600 m3 of biogas per day,about 55–60 percent of which is methane. Other gases producedduring the digestive process include carbon dioxide (approxi-mately 40 percent) and a small amount of hydrogen sulfide.

The biogas passes through a series of pipes to the generatorstation, where a diesel engine converted to run on methane drivesa 130-kW generator. The generator powers the farm by produc-ing about 80 kW of three-phase 208-V electricity around the clock.About a year after his visit to Mason Dixon, Aman’s farm beganproducing electricity. Now he sells 10–20 percent of what he pro-duces back to the grid in the summer, when fans used to cool thecows push power usage on the farm to its peak. In the winter, any-where from 35 to 40 percent of the electricity goes to the grid.

After about 40 days in the digester, the waste is pumped intoa separator, which divides the solids from the liquid. The almostodorless effluent is sent to a lagoon lined with a 5-mm-thickpolymer membrane that prevents any seepage into the watertable. From the lagoon, the nutrient-rich liquid is pumpedthrough a 6.5-km-long pipe to alfalfa and corn fields that Amanowns on the other side of town. The processed solids, which are99.8 percent free of bacteria, are composted and then sold toconventional and organic farms, which pay around US $22/m3.

AA Dairy is a study in sustainable agriculture as it can bepracticed by the ordinary farmer, as Aman likes to say. But it isextraordinary enough to have attracted the attention of CornellUniversity professor Norman R. Scott, who is investigating thefeasibility of replacing Aman’s current diesel-engine cogenera-tion system with a more efficient molten-carbonate fuel cell.

With a little help from the Swedes

Fewer than 100 digester-powered farms of all types exist in theUnited States, but the list is growing. Within the last year,another, larger operation has cropped up in Homer, N.Y., aboutan hour’s drive from AA Dairy. Dairy Development Interna-tional (DDI) is a joint venture between the Feed AnalysisResearch Management Education (Farme) Institute, Homer,N.Y., and DeLaval International AB, of Tumba, Sweden, whichhas half the worldwide market in milking machine equipment.

For a place that houses 850 Holsteins, DDI looks strangelyclean. One reason is that the $5.5 million farm is brandnew—it started milking cows only in August 2001. It’s also alaboratory. The Farme Institute is a contract research organ-P

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ization founded by Lawrence R. Jones, who has a Ph.D. indairy science and a background in artificial intelligence andcontrol systems. The research conducted at DDI will affectdairy farming practices around the world. In fact, DeLavalinvested in the upstate New York location because of its greatsimilarity, climatically and geographically, to many EasternEuropean countries, such as Estonia, Hungary, and Poland,where DeLaval hopes its dairy farming technologies willincrease milk production.

DDI is Aman’s farm writ large, underwritten as it is by cor-porate funding and government grants. “We mimic manythings we’ve seen from Aman’s farm,” said Jones.

They’ve also made some improvements. For instance, eachof DDI’s three barns will be warmed by water pipes running

under the concrete floor. The hot water, which will be heated bybiogas power, will keep the manure flowing into the digester evenin the dead of winter. So the electricity will keep flowing, too.

That electricity will be generated by four microturbines fromCapstone Turbine Corp., Chatsworth, Calif. [see “NetworkingAssets,” IEEE Spectrum, January 2001, p. 84]. These miniaturegas-fired turbines, which rotate at 96 000 rpm, are more reliableand efficient than the diesel engine used for cogeneration atAman’s farm. There, the hydrogen sulfide in the biogas con-taminates the engine’s lubricating oil and necessitates a weeklyoil change. Microturbines, by contrast, have no liquid lubricants,hence no contamination. But DDI will still scrub the gas beforeit goes to the microturbines by passing it through iron-impreg-nated wood chips (Aman is looking at doing this, too). If the bio-

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Recycling Waste for PowerIn a digester installation, a manure slurry flows from the barn (1) to a receptacle where a pump (2) periodically passes it to

the digester (3). Bacteria break down the manure, releasing gas, which is fed to a generator (4a), which supplies electricity to

the farm. Dairy Development spreads the digested slurry on its land. AA Dairy separates out solids for compost(4b, 5b) and

pumps the liquid to a lagoon (4c) where it is held until sprayed on crops (5c) used to feed the cows (1, again). It sells excess

power back to the grid (5a).

Spray

Feed

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Solids truck under separator

Milking parlor

Pump to digester

CRITICAL CHALLENGES 2002

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Barn

Compost heaps

Lagoon

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gas is not scrubbed, the sulfur could precipitate out of the exhaustas an acid, a danger for surrounding equipment as well as thefarm’s 12 000 m2 of aluminum roofs.

When Spectrum toured the facility early last November,DDI was still in the start-up phase. While manure was flow-ing into the digester, the gas produced was being flared, orburned off, and the microturbines were on-site but not yet inservice. Jones expected them to be up and running by the endof December. When the microturbines go on-line, they will befed a steady stream of biogas and will produce a total of 100 kWof 480-V electricity. This voltage permits the electricity to betransmitted and used without any reliance on transformers.

The lessons learned at both AA Dairy and DDI could go fartoward helping the entire livestock industry deal with animal

waste, according to Cornell’s Scott. In the future he envisionshuge digester facilities for rural areas. “There are actuallycommunities here in New York talking about what they call a community digester,” said Scott, who estimated that if all themanure produced on half of the largest of the dairy farms inNew York were put through digesters, the resulting electricitycould power all participating farms, plus 60 000 homes.

Chemical impact on groundwater

Manure pollution is conspicuous. But the effects of agriculturalchemicals on our water and our bodies are subtler and are onlynow being rigorously investigated.

The latest report published by the National Water-QualityAssessment (NAWQA) Program of the U.S. Geological Survey(USGS) states that farming accounts for 70–80 percent of themore than 450 000 000 kg of pesticides used in the UnitedStates each year. USGS researchers found at least one pesticidein almost every water and fish sample collected from streamsand in more than one-half of the shallow wells sampled in bothagricultural and urban areas. One-half of the samples fromwells contained two or more pesticides, one-quarter containedfour or more. While concentrations of these chemicals werealmost always lower than current U.S. EPA drinking-water stan-dards, these exist for only 46 of the 83 pesticides measured. Fur-thermore, current standards do not take into account exposureto the chemical cocktails found by NAWQA—for example,atrazine, metalochlor, and nitrate—nor do the guidelines con-sider seasonal spikes in chemical usage.

Some of the most frequently detected pesticides are sus-pected endocrine disrupters that could harm reproduction ordevelopment of aquatic organisms or wildlife by interferingwith natural hormones. In fact, more than one-half of agricul-tural and urban streams sampled had concentrations of at leastone pesticide that exceeded a guideline for protection of aquaticlife. “In addition, potential effects on reproductive, nervous, andimmune systems, as well as on chemically sensitive individu-als, are not yet well understood,” NAWQA reported in 1999.

That’s a polite understatement. While something is knownabout the effects of pesticides on fish, precious little is knownabout these same pesticides’ effects on people. The good newsis that a major study of the potential health effects on humansis now under way. The National Report on Human Exposure toEnvironmental Chemicals sponsored by the U.S. Centers forDisease Control and Prevention, in Atlanta, Ga., is looking at27 environmental chemicals, including six organophosphatepesticide metabolites (breakdown products) such asdimethylphosphate and diethylphosphate, by measuring thechemicals or their metabolites in blood or urine samples. Tohelp track exposures over time, an updated version of thereport will be published every 12–24 months and will eventu-ally cover more than 100 chemicals.

Soil stewardship

One effective way to minimize agricultural water pollution isto eschew chemicals altogether, as with organic farming. “Youdon’t have those soluble fertilizers and nitrates leaching into thewater table,” said Eugene B. Kahn, president and CEO of Gen-

Liquid

Solid

Gas

Digested manure

Digested manure

AA Diary’s excesselectricity sold to grid

Liquids separatedfrom solids

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Generator AA

Digester

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eral Mills’ Small Planet Foods, Sedro-Woolley, Wash., andfounder of organic food giant Cascadian Farm. “We feed thesoil, and that by definition leads us more toward sustainability.”

There are many views on what makes for sustainable agri-cultural practices. The techniques championed by Kahn excludethe use of herbicides or insecticides. But Jonathan Moscatello,agricultural program manager for the Portland, Ore.–basedFood Alliance, sees no problem with using herbicides in lim-ited amounts, provided that the soil is not tilled. His view is allthe more intriguing because the Food Alliance has developedstrict standards for certifying farming practices that they believeconserve and protect soil and water resources.

Plowing oxygenates much of the active organic matter in thesoil, killing many of the beneficial organisms, Moscatello con-tends. With the no-till technique, the stubble and stalks are lefton the ground after the fall crop is harvested. Over the winter,weeds might start sprouting. When spring comes and it’s plant-ing time, the farmer sprays the land with a broad-spectrum her-bicide to kill all the weeds, which add to the crop residue left from

the fall harvest. The farmer then uses a special no-till planter toinsert seeds through the overlying residue and into the soil.

Moscatello claims that no-till yields soil that is richer inorganic matter. Such soil transfers chemicals to plants moreefficiently, so that a farmer can use less herbicide and fertilizer.The result is less pollution of ground or surface water.

Some researchers disagree with Moscatello about the efficacyof no-till techniques in protecting water from chemical con-tamination. One study conducted by USGS in cooperation withthe University of Tennessee on farms in the Beaver Creek Water-shed in West Tennessee concluded that when compared withconventional tillage methods, no-till methods made no differencein the amount of chemicals that leach into groundwater. Thatsame study also pointed out that “no-tillage has proven to be aneffective BMP [best management practice] for soil-loss reductionin many studies throughout the United States.”

Indeed, no-till, as well as crop rotation (sowing the same fieldwith a different crop every year), are so effective at conservingtopsoil that the practices are now heavily advocated by interna-

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KCRITICAL CHALLENGES 2002

The World Health Organization con-

servatively estimates that today

1.1 billion people, mostly poor and liv-

ing in rural areas, cannot meet their needs

for safe water. That number could triple by

2025, a grim prospect considering that

today close to two million children die every

year from diarrheal diseases caused by

waterborne organisms.

At first glance, providing enough clean

water for such a vast number of people in the

world’s poorest regions might seem impos-

sible. But experts say the solution need be

neither expensive nor terribly complicated.

Consider the program in rural Western

Kenya jointly sponsored by the U.S. Centers

for Disease Control and Prevention (CDC)

and the nongovernmental organization

CARE International, of Brussels, Belgium. In

2001, the project, funded to the tune of

US $200 000, began cleaning up the water

by introducing the Safe Water System

(SWS) in 72 villages housing 43 000 people.

The approach is simple: treating the

water with a cheap disinfectant, safely stor-

ing the water in the home, and most impor-

tantly, changing relevant behavior.

The disinfectant is a solution of 1 per-

cent sodium hypochlorite, a chlorinating

disinfectant. It is sold under the brand

name Klorin and produced for CARE by a

local chemical company that sells the

500-ml bottles for US 33 cents each. The

Klorin bottle cap doubles as a measuring

device, so people need no other implement

with which to dose their water.

For storing water, project workers initial-

ly tried introducing plastic jugs. Most

Kenyans in the project area, though, pre-

ferred the traditional clay vessel, with a wide,

open mouth into which people dip a cup to

scoop up water. But that runs the risk of

recontamination if the dipper, or hand holding

it, is dirty. The problem was solved when

Kenyan CARE workers, led by Sam Ombeki,

Paul Ogutu, and Philip Makutsa, teamed up

with a local group of women artisans to pro-

duce a supply of modified clay pots with nar-

row mouths, lids, and spigots at the bottom.

For US $2.50 apiece, villagers can now buy

clay vessels that keep the water clean, cool,

and fresh tasting.

Changing people’s behavior was the

trickiest part. For that, the CARE/CDC team

used marketing tools such as Klorin-

themed posters, banners, and T-shirts of

the “Klorin Is Good for You” variety. These

were often distributed at promotional

events such as puppet shows and soccer

tournaments, where dancers dressed in

Klorin bottle costumes would also appear.

“It’s very simple,” said Robert Quick, a

medical epidemiologist with the Foodborne

and Diarrheal Diseases Branch of CDC.

“People who can’t read or write you

teach with pictures and you tie it in to the

commercial sector.”

The campaign is making headway. Some

33.5 percent of households have adopted

the Klorin treatment and 18.5 percent have

bought the modified clay pots. Overall, the

homes that used Klorin and the new vessels

showed a 58 percent decline in diarrhea

and related illnesses in the six months fol-

lowing adoption of the system.

CDC and CARE would like to expand the

project to all of Kenya. Furthermore, accord-

ing to Quick, the Safe Water System is making

inroads in several other developing countries,

including Madagascar, Uganda, South Africa,

Zambia, Bolivia, Ecuador, and Peru, with more

projects set for launch soon in Tanzania, India,

and Togo. –H.G.

Safe Water Saves Lives

Artisans from the Oriang Women

Pottery Group, Nyanza Province,

Kenya, display water storage vessels.

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tional agencies like the United Nations’ Food and AgricultureOrganization (FAO). Such conservation agriculture, as the FAOcalls it, is being adopted, albeit slowly. Of the 1.5 billion hectares(15 million km2) of land farmed worldwide, the organizationestimates that conservation agriculture is being practiced ononly 58 million hectares, including around 20 million hectaresin the United States, 13.5 million hectares in Brazil, 9.5 millionhectares in Argentina, 4 million hectares in Canada, and about800 000 hectares in Paraguay.

What drives change?

In developed countries, any drive to cultivate more land usingconservation agriculture will in the end come from consumers,whose demand for organic food has for a decade been growingat 15–20 percent per year in the United States and much fasterin Europe. This trend has attracted the interest of large food com-panies and prompted General Mills to acquire Kahn’s SmallPlanet Foods in 2000. “As a consumer-driven food company,General Mills wants to stay on top of consumer trends and meetconsumer need,” Kahn told Spectrum.

While Kahn contends that to those who choose it, organicfood is “just lunch,” leading consumer advocate Andrew Kim-brell, director of the Center for Food Safety, Washington,D.C., believes that people realizethat “every food decision they makehas implications for the earth.”And, he added, “They’re voting withtheir consumer dollar for technolo-gies, techniques, and foods thatreflect their new consciousnessabout their own personal health andthe health of the natural world.”

Consumers who can pay pre-mium prices for organic food mayhave some say in how certain cropsare cultivated, but will have less tosay in addressing the 1.36 trillionkilograms of animal waste producedby eight billion U.S. farm animals. Solutions to that problemwill likely depend on regulatory imperatives and governmentincentives. The EPA’s AgSTAR program is one step down a trailblazed by European countries like Denmark, where the gov-ernment entices farmers to produce power from biogas byallowing them to sell excess power back to the grid at pre-mium prices. For now, U.S. farmers seem more concernedabout the government eventually compelling them to deal withtheir animal waste in a more efficient manner. Some farmershave told Cornell’s Scott that they are investigating digesters notonly because they view themselves as the ultimate stewards ofthe land, but also because they want options if and when anynew environmental regulations come down the pike.

Larger dairy and swine farms are particularly interested,Scott noted, and these are the kinds of operations that canafford to buy efficient, technologically sophisticated power gen-erators like microturbines. In fact, one of Scott’s students hasjust left Cornell to run a 4000-head dairy operation in Califor-nia that will be installing microturbines. Scott suggests that,

once prices for advanced cogeneration systems drop into linewith farmers’ wallets, farms could become a lucrative nichemarket for microturbines and even for fuel cells.

Other market opportunities in sustainable agriculture arecurrently being exploited by farm equipment manufacturerslike Yetter Manufacturing Co., Colchester, and John Deere & Co.,Moline, both in Illinois. Bob Nelson, a spokesman for JohnDeere, said that the company has been making planting equip-ment for farmers who over the last 20 years have been attractedto the no-till method, and he stressed that the company contin-ues to develop the technology. Deere is also building global posi-tioning system (GPS) receivers into its tractors and combines tohelp farmers plant, spray, and harvest more precisely, cutting theamounts of chemicals applied and fuel used. Nelson estimatedthat 10–20 percent of U.S. farmers already use GPS as part of anoverall precision agriculture approach and that their ranks are“growing every day as the systems improve.”

In poor and developing countries, though, changes in agricul-tural practice will have less to do with tractors equipped with thelatest bells and whistles or consumers demanding organic toma-toes than with getting the most out of the land as cheaply, and withas little soil degradation, as possible. Fertile soil and clean water areprecious commodities in countries struggling to feed their people

[see “Safe Water Saves Lives,” oppositepage]. Conservation agriculture andminimum tillage in particular havebeen proven to prevent topsoil erosion.Moreover, by not tilling the soil, farm-ers can save between 30 and 40 percentof time, labor, and fuel costs comparedto conventional cropping, accordingto the United Nations’ Food and Agri-cultural Organization.

Conservation agriculture for cropcultivation can work equally well inboth the developed and developingworlds. For livestock operations suchas dairy farming, however, one per-

son’s sustainable solution can be another’s ticket to destitution.Aman tells the story of a visitor from India who recently

toured his farm. Since the mid-1970s, the Indian government hasbeen supporting the installation of anaerobic digesters in rural,cow-owning households as an alternative to wood and kerosenefor cooking and heat. But when Aman suggested his visitor builda modern dairy based on AA’s design, he politely demurred. Inhis opinion, the Indian government would never sanction suchan operation because the socioeconomic costs are too high.

Approximately 70 million Indians eke out a living from dairycows. Not only would a highly efficient, industrial dairy farmsuch as Aman’s be beyond the means of even most wealthyIndian farmers, but such operations, if they were to proliferate,would also rob millions of subsistence. In developing coun-tries like India, the implementation of sustainable agriculturaltechniques often involves striking a balance between ensuringlocal self-sufficiency and protecting the water supply, and con-trolling the dissemination of technology in such a way that itsupplements human labor without replacing it entirely. •M

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Organic farmers enrich the soil

with compost like this from AA Dairy.