Municipal Solid Waste (MSW) Digesters

Using anaer­o­bic digesters for high­ly con­t­a­m­i­nat­ed waste streams like munic­i­pal sol­id waste is very prob­lem­at­ic, since the result­ing prod­uct can­not be clean enough to be use­ful. Using expen­sive meth­ods like in-ves­sel com­post­ing or diges­tion to han­dle munic­i­pal sol­id waste caus­es the own­ers to seek to find mar­kets for the result­ing “com­post.” In fact, most munic­i­pal sol­id waste com­post­ing projects have a hard time find­ing a mar­ket for their “com­post” prod­uct and end up giv­ing the “com­post” away to farm­ers, using it on pub­lic works projects or as land­fill cover.

Below are 2 arti­cle from Decem­ber 2004 about an attempt to use digesters to process munic­i­pal sol­id waste in north­cen­tral Pennsylvania.

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Scientists test organic waste technology

Trash may soon become trea­sure. Uni­ver­si­ty researchers are test­ing sev­er­al tech­nolo­gies they hope will trans­form waste into use­ful byprod­ucts like fer­til­iz­er and methane gas.

Asso­ci­at­ed Press

WILLIAMSPORT, Pa. — Lycoming Coun­ty offi­cials and sci­en­tists are test­ing tech­nol­o­gy they hope will turn organ­ic waste into prof­itable byproducts.

One of the tech­nolo­gies, a met­al tank called a Drygester, is designed to break down organ­ic waste anaer­o­bi­cal­ly — with­out oxy­gen. Man­u­fac­tured by Young Indus­tries in Muncy, it is one of six sys­tems Buck­nell and Van­der­bilt Uni­ver­si­ty researchers are test­ing in con­junc­tion with coun­ty engi­neer Michael D. Hnatin.

The tests will deter­mine which sys­tem will be used in the land­fil­l’s pilot pro­gram. The plant would biode­grade up to 30 tons of munic­i­pal sol­id waste per day that pre­vi­ous­ly would have been buried in the landfill.

Byprod­ucts would include methane gas, usable for fuel, and a type of fertilizer.

Hnatin said the process is sim­i­lar to what occurs nat­u­ral­ly in the land­fill as organ­ic mate­r­i­al decom­pos­es deep with­in the mounds of garbage. How­ev­er, the nat­ur­al process requires 20 to 30 years; a Drygester-type sys­tem should take about 20 to 30 days.

The land­fill plans to sub­mit a per­mit appli­ca­tion for the pilot plant to the state Depart­ment of Envi­ron­men­tal Pro­tec­tion by April, Hnatin said. It will cost the land­fill rough­ly $3 mil­lion to $5 mil­lion to build the pilot plant, he said.

The Drygester pro­to­type process­es only 15 pounds of waste dai­ly but the diges­tion tank planned for the pilot plant could process up to 30 tons a day, Hnatin said.

Offi­cials esti­mate the coun­ty’s land­fill will be full and will have to close by mid-2011. Anaer­o­bic pro­cess­ing would increase the its life as much as 10 per­cent by reduc­ing the amount of waste buried there, Hnatin said.

The project is part of the coun­ty com­mis­sion­ers’ Green Tech­nol­o­gy Initiatives.

Sto­ry pro­duced by Lau­reen Ricks
Source: http://iml.jou.ufl.edu/newszine/tech/2.htm

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Meet the ‘Drygester’

Pilot project at land­fill uses inno­v­a­tive sys­tem to con­vert raw garbage into ener­gy, fertilizer

San­dra M. Huff
Sun-Gazette Staff

Offi­cials hope a met­al tank that sits in one of the coun­ty land­fil­l’s ware­hous­es will help con­vert up to 75 per­cent of the land­fil­l’s organ­ic waste into mon­ey some day.

The tank is referred to as the “Drygester” and is designed to digest organ­ic waste “anaer­o­bi­cal­ly” ­ with­out oxy­gen. Man­u­fac­tured by Young Indus­tries in Muncy, the Drygester is one of six sys­tems being test­ed by researchers at Buck­nell and Van­der­bilt Uni­ver­si­ty in con­junc­tion with Lycoming Coun­ty Resource Man­age­ment Ser­vices engi­neer Michael D. Hnatin.

The tests will deter­mine which sys­tem will be used in the land­fil­l’s future pilot plant to pro­vide an alter­na­tive way of break­ing down waste.

The plant would be the first of its kind in the coun­try and would biode­grade up to 30 tons of munic­i­pal sol­id waste per day, waste that pre­vi­ous­ly would have been buried in the land­fill. Among the byprod­ucts will be methane gas, usable for fuel, and “soil con­di­tion­ers” ­ a sort of fertilizer.

Hnatin said the anaer­o­bic diges­tion process imi­tates what occurs nat­u­ral­ly in the land­fill as organ­ic mate­r­i­al decom­pos­es deep with­in the mounds of garbage. How­ev­er the nat­ur­al process requires 20 to 30 years, where­as a Drygester-type sys­tem should take about 20 to 30 days. Hnatin said that’s because the waste will be digest­ed in an air­tight con­tain­er under con­trolled conditions.

Hnatin said the land­fill plans to sub­mit a per­mit appli­ca­tion for the pilot plant to the Depart­ment of Envi­ron­men­tal Pro­tec­tion by April 2005. Approval is expect­ed by 2006, and con­struc­tion of the pilot plant should take about two years. Hnatin said its effi­cien­cy will then be mon­i­tored for two years to deter­mine whether a larg­er plant should be built.

The Drygester only process­es 15 pounds of waste a day, but the diges­tion tank planned for the pilot plant will be able to process up to 30 tons a day, Hnatin said.

It will cost the land­fill rough­ly $3 mil­lion to $5 mil­lion to build the pilot plant, Hnatin said.

Hnatin said sev­er­al facil­i­ties in Europe have been using the process of anaer­o­bic diges­tion for years, but Amer­i­ca has yet to imple­ment what he called a mon­ey-sav­ing, ener­gy-effi­cient method of deal­ing with its garbage.

“The anal­o­gy we like to use is that it’s like a waste-water plant,” Hnatin said.

He explained that anaer­o­bic diges­tion can replace land­fills just like the out­hous­es of the past became obso­lete when mod­ern sew­er sys­tems were introduced.

So far the land­fill has received $157,000 in grant mon­ey for the project from the state Depart­ment of Envi­ron­men­tal Protection.

Offi­cials esti­mate the land­fill can oper­ate until mid-way through 2011. At that point it will have reached its lim­it it will need to close.

Anaer­o­bic pro­cess­ing, how­ev­er, will increase the longevi­ty of the land­fill by up to 10 per­cent by cut­ting down on the amount of waste buried there, Hnatin said.

The process will also increase the amount of mate­ri­als recy­cled. Hnatin said that one of steps in the process screens out recy­clable goods that can then be sent to the land­fil­l’s recy­cling facility.

Increas­ing the longevi­ty of the land­fill eas­es the bur­den on tax­pay­ers, who will have to dole out funds to main­tain it when it closes.

Hnatin said that munic­i­pal­i­ties are required to main­tain a land­fill for 30 years after it clos­es, at an aver­age cost of about $8,000 a year.

“No one likes a land­fill in their back yard, and they’re expen­sive to keep up,” Hnatin said. “(Anaer­o­bic diges­tion) makes it into a process, not a lia­bil­i­ty for our kids and grandkids.”

Hnatin said the methane pro­duced by anaer­o­bic pro­cess­ing can be sold to pow­er plants. Also pro­duced is a sub­stance that Hnatin said looks like pot­ting soil and has an “earthy smell.”

The sub­stance is “soil amend­ment” or “soil con­di­tion­ers,” and can be sold commercially.

Hnatin also said the land­fill is work­ing with two cor­po­ra­tions with­in the state on the pos­si­bil­i­ty of pro­duc­ing liq­ue­fied nat­ur­al gas from the process.

He said if the 26,000 oth­er land­fills in Amer­i­ca fol­lowed in the coun­ty land­fil­l’s foot­steps with anaer­o­bic diges­tion, it would make the nation less depen­dent on for­eign ener­gy providers.

The project is part of the coun­ty com­mis­sion­ers’ Green Tech­nol­o­gy Initiatives.

Sec­tion: News
Date Post­ed: 12/5/2004

As appear­ing in Sun­day — Decem­ber 5, 2004 edi­tion of The Sun-Gazette