[USCC] Alaska Composting

[Jim McNelly]

>From Environmental News Network, 8-14-06. Cold Can't Stop Alaska 
>Sewage Composting.  FAIRBANKS, Alaska - Environmental consultant 
>Mike Pollen remembers standing on a pile of sewage sludge composting 
>outside the Fairbanks treatment plant on a November day in 1997. The 
>temperature was 40 degrees below zero but his feet were warm. Then 
>sweaty. Then uncomfortably hot inside his insulated rubber boots. 
>"They felt like they were going to melt," he said.He figures there 
>was a 180-degree difference between the compost cooking at his feet 
>and the frosty temperature freezing his head.Prevailing wisdom said 
>sludge composting wouldn't work north of North Dakota. Pollen, the 
>author of several wastewater system training manuals used in Alaska, 
>remembers turning to a utility official and remarking, "You know 
>what you just did? You just rewrote the textbook."
>
>Over the years, utility officials in the community 120 miles south 
>of the Arctic Circle continued "aerated static pile composting" and 
>now turn waste from 87,000 residents into a product so highly 
>desired they can't make enough to satisfy requests from gardeners 
>and landscapers who want to amend their sub-Arctic soil."It's 
>something we think is a big hit," said Dave Dean, support services 
>manager for Utility Services of Alaska.  The compost, cooked in beds 
>bigger than football fields, has the EPA's highest rating. 
>Cooperative extension officials recommend it for growing vegetables 
>as well as flowers and grass. The price is right -- just $15 per 
>pickup load or $5 per yard dropped into dump trucks -- and it's free 
>to anyone with a shovel and a trash can.But merely getting sludge 
>off the premises has been a triumph for the second largest community 
>in Alaska, where winter routinely lasts seven months and the severe 
>cold can make life miserable for microbes.
>
>Sewage sludge is the solid material removed from water that flows 
>into a treatment plant -- 15 gallons at a time from a dishwasher, 
>31.5 gallons per 6.3-minute shower, 1.5 gallons per flush. Treatment 
>plants strive to separate solids from liquids, then deal with each 
>separately.Rich in nutrients, raw sludge also can be filled with 
>dangerous pathogens or heavy metals that must be addressed before it 
>can be applied to fields, burned, or even buried in a landfill. 
>There are plenty of ways to neutralize human waste but utility 
>companies are constrained by time, space and money.If they choose a 
>process that's slow, they end up stockpiling sludge, where it's 
>attacked by anaerobic bacteria that produce offensive odors. For 
>many aerobic processes, abundant space is needed, unless a utility 
>has cash for equipment that can speed or automate decomposition.
>
>The Fairbanks plant itself is designed for the cold. It's one of the 
>few in the country that's fully enclosed, allowing treatment in huge 
>tanks all year round. The plant pumps pure oxygen into its digester, 
>speeding the work of helpful bacteria that turn raw sludge into 
>digested sludge.In the early 1980s, when the EPA enforced new water 
>quality laws, Fairbanks was banned from hauling digested sludge to 
>its landfill. The utility, then owned by the city, instead merely 
>stored it outside the plant.When the utility ran out of storage 
>space, it built a lagoon with 20-foot high walls. That filled up 
>too, and utility officials launched a half-dozen attempts to address 
>their sludge trove.
>
>A contractor burning pure sludge produced putrid clouds that hung 
>near the ground during winter temperature inversions. Operators 
>tried mixing sludge with lime, which neutralized the pathogens but 
>made a product that had the consistency of toothpaste and wouldn't 
>mix with soil.Finally, just before the utility was sold to private 
>investors, operators began experiments with composting.Digested 
>sludge is run through a press to mash out water. Still, the sludge 
>is 80 percent liquid when it's moved outside by conveyor to a dump 
>truck.That's where Jeff Karrick, one of three full-time compost 
>operators, comes in. Karrick is a master of mega-mixology with a 
>front-end loader, his measuring cup a 4-yard bucket, his "bin" the 
>flat ground outside the plant.
>
>Like any home composter, he mixes digested sludge, a "green" 
>material rich in nitrogen and phosphates, with a carbon source that 
>feeds bacteria, provides bulk to let in air and absorbs moisture 
>from the sludge. The utility uses fresh wood chips obtained from the 
>only sawmill in the Fairbanks North Star Borough, plus partially 
>decomposed wood chips screened from older compost piles.Karrick 
>dumps 16 yards of used wood chips onto 16 yards of new chips, then 
>adds 14 yards of sludge. With his heavy equipment, he attacks the 
>pile from all sides, lifting, dropping and mixing until the material 
>is homogenous. Then, on top of perforated pipe that delivers air, he 
>stacks the mix against the main pad, creating a massive 9-foot-high 
>sludge and wood chip cake that when completed will be 120 feet wide 
>and 360 feet long.
>
>Operators frost the top and sides with 2 feet of composted material. 
>The topping keeps odors and nasty clouds of blowflies at bay. 
>"That's our biofilter," Karrick said. The extra layer is also the 
>key to the success of cold weather composting, said Nora Goldstein, 
>executive editor of BioCycle magazine and a member of the Water 
>Environment Federation, a national nonprofit organization focused on 
>clean water.In the extreme cold, Goldstein said, bacteria could slow 
>or shut down. That's not bad, unless it forces a utility to 
>stockpile sludge. "So much of that depends on the composition mix 
>and the insulation of the pile," she said.
>
>Temperature probes detect some cooling in the coldest weather but 
>extra fresh wood chips keep the pile hot enough to let operators add 
>to the pad all winter long -- and never stockpile sludge. EPA 
>requires the compost to cook at 104 degrees for 14 consecutive days. 
>For three consecutive days, the temperature must reach at least 131 
>degrees so pathogens will be killed.The highest temperature recorded 
>in a Fairbanks pile was 206 degrees. "I'm thinking of digging a hole 
>and dropping a pig in there," Karrick joked.
>
>When the piles attain the required temperatures, the stack -- now 
>just 8 feet fall because of the shrinkage in the composting process 
>-- is run through a screening machine to take out wood chips that 
>didn't process. EPA allows up to 1,000 fecal coliform bacteria per 
>gram dry weight of compost. Tests of finished compost often don't 
>detect any. Fairbanks has little manufacturing and solids entering 
>the plant contain little heavy metal such as arsenic and lead. The 
>official EPA rating for the compost is "exceptional quality."The 
>product has been around long enough that most gardeners have 
>overcome their repugnance of using a product made from human waste.
>
>Michele Herbert, land resources agent for the University of Alaska 
>Fairbanks Cooperative Extension Service, recommends the compost to 
>gardeners and has used it herself to grow vegetables, mulch 
>perennial beds and landscape."It's crazy, the stuff is so good," she 
>said.In contrast, the city had to pay more than $400,000 to 
>neutralize and move the 50,000 cubic yards of sludge that had 
>accumulated over 20 years before a solution was found.Dean, the 
>utility support services manager, said the company is not making 
>money off compost. It charges enough to defray its cost of 
>loading.But operators are clearly proud that they've solved their 
>sludge problem by taking something nobody wants and turning it into 
>a desirable commodity.