COMPOSTABLE

The?right?to?use?the?mark?of?conformity?"COMPOSTABLE"?on?compostable?plastic?bags?and?on?compostable?products?is?granted?only?to?those?manufacturer/distributors?that?demonstrate?that?their?product?conforms?with?specific?performance?attributes?and?adheres?to?the?parameters?for?"compostability"?as?set?out?in?the?BNQ?documents,?Compostable?Plastic?Bags?-?Certification?Program?

(BNQ?9011-911/2007)?and?Compostable?Products?–?Certification?Program?(CAN/BNQ?0017-988).?

It?is?important?to?be?aware?that?"compostable"?and?"biodegradable"?are?not?equivalent.?Similarly,?"disintegration"?cannot?be?used?interchangeably?with?either?of?these?terms.

The?definitions?established?for?the?purpose?of?the?program?are?as?follows:

Biodegradation:?degradation?caused?by?biological?activity?especially?caused?by?enzymatic?action?leading?to?a?significant?change?in?the?chemical?structure?of?a?material.?(Reference:?ISO?162929,?section?3.3)?

Compostable:?said?of?that?which?is?capable?of?undergoing?biological?decomposition?in?a?compost?site?such?that?the?material?is?not?visually?distinguishable?and?breaks?down?into?carbon?dioxide,?water,?inorganic?compounds?and?biomass?at?a?rate?consistent?with?known?compostable?materials.?(Reference:?ASTM?D?6002)?.

Degradation:?an?irreversible?process?leading?to?a?significant?change?in?the?structure?of?a?material,?typically?characterized?by?a?loss?of?properties?(eg.?integrity,?molecular?mass?or?structure,?mechanical?strength)?and/or?by?fragmentation.?Note:?degradation?is?affected?by?environmental?conditions?and?proceeds?over?a?period?of?time?comprising?one?or?more?steps.?(Reference:?ISO?16929,?section?3.2)?

Compost:?solid?mature?product?resulting?from?composting?(Reference:?CAN/BNQ?0413-200)?

Composting:?managed?process?of?bio-oxidation?of?a?solid?heterogeneous?organic?substrate?including?a?thermophilic?phase.?(Reference:?CAN/BNQ?0413-200)?

Compostable?plastic?bags?and?compostable?products?must?be?compatible?with?the?dynamics?invo*ed?in?the?composting?process?and?not?detract?from?the?physical?and?chemical?quality?of?the?end?product,?compost.?

In?Canada,?for?a?plastic?bag?or?other?product?to?claim?compostable,?it?must:

??★disintegrate?by?at?least?90%?within?84?days?of?the?composting?process?

??★biodegrade?by?at?least?90%?within?180?days?of?the?composting?process?

??★have?no?ecotoxicological?effect?greater?than?10%?on?the?germination?rate?of?seeds?and?

??★vegetation?biomass?rate?

CRITERIA-?Background

The?process?to?establish?the?Canadian?criteria?for?the?evaluation?of?claims?for?compostable?plastic?bags?originated?because?of?plastic?bags?being?introduced?into?the?Canadian?marketplace?using?compostable?claims?that?were?not?valid?(ie.?they?were?not?compostable).

Originally?initiated?for?Québec?purposes?by?Recyc-Québec?and?the?City?of?Montréal,?the?development?of?the?Canadian?Certification?Program?for?compostable?plastic?bags?was?expanded?nationally?by?The?Composting?Council?of?Canada?with?support?from?the?provincial?ministries?of?environment?of?New?Brunswick,?Prince?Edward?Island,?Nova?Scotia,?Manitoba?and?Alberta.

The?Bureau?de?normalisation?du?Québec?(BNQ),?having?had?past?experience?in?standard-setting?for?the?composting?industry,?was?commissioned?to?coordinate?the?review?process.

Rather?than?re-inventing?the?wheel,?the?review?process?invo*ed?the?examination?of?existing?international?standards?for?compostable?plastic?bags?and?evaluating?their?appropriateness?for?Canadian?conditions?as?well?as?composting?facility?operational?and?product?marketing?requirements.

A?15-person?review?panel?was?selected?invo*ing?representatives?from?municipalities,?composting?facilities,?product?suppliers?and?users?as?well?as?consumer?groups.?Following?extensive?discussion?as?well?as?public?consultation,?the?Canadian?Certification?Program?became?official?in?September?2007.

In?2010?the?certification?program?was?expanded?to?include?compostable?products?of?all?types,?following?the?adoption?of?the?standard?CAN/BNQ?0017-988.?This?serves?to?adopt?the?standard?ISO?17088?as?the?national?standard?for?Canada.?It?is?important?to?note?that?the?original?program?for?the?certification?of?compostable?plastic?bags?(BNQ?9011-911/2007)?will?soon?be?cancelled?to?be?replaced?entirely?by?the?certification?program?for?compostable?products?(CAN/BNQ?0017-988).

Time?and?rate?of?degradation?and?disintegration?were?amongst?the?criteria?established.?Requirements?for?the?bags'?impact?on?the?finished?compost?from?the?perspective?of?visual?quality?as?well?as?trace?element?content?and?plant?exotoxicity?have?also?been?established.?The?final?set?of?criteria?selected?reflects?the?operational?and?regulatory?realities?which?composting?facilities?must?adhere?to?in?Canada?for?both?organic?residuals?processing?and?finished?compost?product?sale.

Those?manufacturers/product?representatives?wishing?to?adhere?to?the?Canadian?Certification?Program?and?use?the?compostable?mark?of?conformity?on?their?compostable?plastic?bags?must?submit?an?application?to?the?BNQ?for?review?and?meet?the?requirements?of?the?program.

Two?review?options?are?available:?

·?Submit?existing?compostability?test?results?from?internationally-
recognized?laboratory?organizations.?These?will?be?reviewed?by?the?BNQ?to?confirm?adherence?to?the?Canadian?Certification?Program.?

·?request?the?BNQ?to?conduct?the?testing?in?internationally-recognized?laboratory?organizations?of?the?selected?product?according?to?the?criteria?set?out?in?the?Canadian?Certification?Program.?

Both?options?have?costs?associated?with?them.?The?manufacturer/product?representative?should?contact?the?BNQ?directly?for?further?details.

Documentation
Copies?of?the?certification?program?documents?for?compostable?plastic?bags?BNQ?9011-911/2007?and?for?compostable?products?CAN/BNQ?0017-088?and?the?certification?protocol?BNQ?0017-988?associated?with??these?programs?can?be?ordered?directly?on?the?BNQ?website.

ABOUT?COMPOSTING

What?is?Composting?
Composting?is?a?natural?process?whereby?micro-organisms?transform?organic?waste?materials?into?a?soil-?like?product?called?humus?(pronounced?"hue-mous").?Kitchen?scraps,?leaves?and?yard?waste,?paper,?wood,?food-processing?wastes,?as?well?as?agricultural?crop?wastes?and?animal?manures,?are?excellent?organic?waste?materials?that?can?be?composted.

Composting?has?a?wide?range?of?benefits:?it?helps?to?reduce?the?amount?of?waste?going?to?landfills?and?produces?a?valuable?product,?compost,?of?benefit?to?soil?health?&?vitality?in?addition?to?many?other?attributes?such?as?water?and?soil?conservation.?It?is?estimated?that?about?40?to?60?percent?of?the?total?waste?stream?could?be?composted!

For?the?composting?process?to?work?best,?it?is?important?that?the?micro-organisms?have?a?continuous?supply?of?food?(i.e.,?organic?wastes),?water?and?oxygen.?As?well,?managing?the?temperature?of?the?composting?material?is?important?to?make?the?process?work.

Although?most?organic?wastes?supply?all?of?the?nutrients?necessary?for?the?micro-organisms?to?grow,?they?grow?best?with?certain?levels?of?carbon?(C)?and?nitrogen?(N).?Paper,?leaves?and?wood?are?high?in?carbon,?while?grass?clippings?and?vegetable?trimmings?are?high?in?nitrogen.?The?materials?in?the?composting?"recipe"?need?to?be?mixed?in?the?correct?combination?to?create?the?right?C:N?ratio.

Types?of?Composting
Composting?can?be?done?in?many?different?ways.?Types?of?composting?range?from?residential?or?backyard?composting?to?mid-scale?and?central?municipal?or?industrial?composting?systems.?Selecting?the?most?suitable?method?depends?on?the?amount?and?type?of?organic?materials?to?be?composted.?

Residential?or?backyard?composting?means?that?an?individual?household?composts?most?of?its?food?and?yard?waste?in?a?container?located?outside?the?home.?Worm?composting?is?a?viable?option?to?compost?kitchen?waste?indoors.?Composting?at?home?is?the?simplest?and?most?cost-effective?method?because?collection,?transportation?and?costs?are?avoided.?People?benefit?directly?from?their?own?efforts?by?producing?a?valuable?additive?for?their?own?garden?soil.?

However,?not?all?food?and?yard?waste?can?be?managed?so?simply.?Organic?material?from?commercial?sources,?such?as?restaurants,?supermarkets,?apartment?buildings?and?food?manufacturers,?needs?to?be?managed?differently.?This?is?where?mid-scale?and?centralized?composting?fits?in.?

Both?mid-scale?and?centralized?composting?invo*es?significantly?larger?quantities?and?a?larger?variety?of?organic?wastes.

Mid-scale?composting?is?the?on-site?management?of?organic?waste?generated?by?a?group?of?people,?such?as?in?an?apartment?complex,?office?building?or?hospital.?This?avoids?the?transportation?of?organic?waste.?Centralized?composting?invo*es?the?collection?and?transportation?of?organic?materials?to?a?special?facility?where?it?will?be?prepared?and?processed?into?compost.

Centralized?Composting?Facilities
The?design?and?set-up?of?a?centralized?composting?site?must?take?into?account?such?factors?as?the?type?and?volume?of?organic?waste,?waste?collection?methods,?sorting,?storage?factors?and?the?end?use?for?the?finished?compost.?Quality?organic?waste?and?good?operating?procedures?ensure?the?production?of?high-quality?compost.

Among?the?most?common?centralized?composting?process?technologies,?in?order?of?increased?technology,?are:

Windrows
Organic?materials?are?placed?in?long?triangular?rows?called?windrows.?Windrows?are?turned?and?watered?occasionally?to?ensure?that?the?micro-organisms?get?an?adequate?supply?of?oxygen?and?that?any?clumps?of?organic?material?are?broken?up.

This?method?is?commonly?used?for?composting?leaf?and?yard?waste,?commercial?food?wastes,?or?such?"specialty?items"?as?shredded?Christmas?trees.?

Static?Aerated?Pile
Organic?waste?materials?are?formed?into?windrows?over?perforated?pipes.?Rather?than?the?windrows?being?turned,?air?is?supplied?to?the?micro-organisms?through?the?pipes.?

Almost?all?municipalities?own?the?necessary?equipment?required?for?centralized?composting?operations?using?windrows?or?static?aerated?piles.?This?means?that?the?capital?costs?are?relatively?low.

In-Vessel
In-vessel?systems?are?either?fully?or?partially?enclosed,?and?can?handle?more?material?in?a?smaller?space?than?windrows?or?static?aerated?piles.?However,?they?tend?to?be?more?costly.?These?systems?provide?better?control?of?aeration,?temperature?and?the?moisture?in?the?organic?materials?being?composted,?all?of?which?result?in?faster?decomposition.

If?necessary,?water?can?be?added?to?maintain?the?correct?moisture?level,?and?air?can?be?pumped?in?to?provide?oxygen?and?to?control?the?temperature.?

Although?different?in-vessel?systems?are?available,?they?are?generally?of?three?basic?types:?channels?or?troughs,?containers?and?rotating?drums?(sometimes?called?tube?digesters).

Channels?(or?Troughs)
The?composting?process?takes?place?in?long?rectangular?troughs?or?channels.?The?organic?waste?materials?are?mixed?so?that?the?clumps?are?broken?up?and?the?material?is?aerated.

Containers
Composting?takes?place?in?closed?containers?that?are?supplied?with?air.?Excess?moisture?and?exhaust?air?are?removed?from?the?containers?to?maintain?ideal?conditions?for?the?micro-organisms?throughout?the?process.

Rotating?Drums?(Tube?Digesters)
Organic?waste?materials?are?added?to?a?drum?which?is?continuously?rotating.?The?rotation?ensures?that?the?micro-organisms?are?constantly?supplied?with?the?oxygen?they?need?and?that?all?of?the?organic?waste?materials?are?exposed?to?them.?The?material?remains?in?the?drum?for?three?to?five?days?and?is?then?transferred?to?windrows?for?final?curing.

Anaerobic?Digesters
Organic?waste?materials?can?also?be?digested?in?an?oxygen-free,?or?anaerobic,?environment?by?micro-organisms?that?do?not?need?oxygen.?The?length?of?time?required?to?digest?the?organic?waste?material?varies?according?to?the?individual?technology?usually?between?two?and?twenty?days.?The?process?produces?humus,?methane?and?carbon?dioxide.?The?methane?is?captured?and?converted?into?energy.?Following?digestion,?the?humus?can?be?transferred?to?windrows?or?another?method?for?final?composting.

Excerpts?from?Centralized?Composting?Helping?To?Complete?The?Carbon?Cycle,?written?by?Susan?Antler?of?The?Composting?Council?of?Canada?on?behalf?of?Environment?Canada.

COMPOSTABLE

The?right?to?use?the?mark?of?conformity?"COMPOSTABLE"?on?compostable?plastic?bags?and?on?compostable?products?is?granted?only?to?those?manufacturer/distributors?that?demonstrate?that?their?product?conforms?with?specific?performance?attributes?and?adheres?to?the?parameters?for?"compostability"?as?set?out?in?the?BNQ?documents,?Compostable?Plastic?Bags?-?Certification?Program?

(BNQ?9011-911/2007)?and?Compostable?Products?–?Certification?Program?(CAN/BNQ?0017-988).?

It?is?important?to?be?aware?that?"compostable"?and?"biodegradable"?are?not?equivalent.?Similarly,?"disintegration"?cannot?be?used?interchangeably?with?either?of?these?terms.

The?definitions?established?for?the?purpose?of?the?program?are?as?follows:

Biodegradation:?degradation?caused?by?biological?activity?especially?caused?by?enzymatic?action?leading?to?a?significant?change?in?the?chemical?structure?of?a?material.?(Reference:?ISO?162929,?section?3.3)?

Compostable:?said?of?that?which?is?capable?of?undergoing?biological?decomposition?in?a?compost?site?such?that?the?material?is?not?visually?distinguishable?and?breaks?down?into?carbon?dioxide,?water,?inorganic?compounds?and?biomass?at?a?rate?consistent?with?known?compostable?materials.?(Reference:?ASTM?D?6002)?.

Degradation:?an?irreversible?process?leading?to?a?significant?change?in?the?structure?of?a?material,?typically?characterized?by?a?loss?of?properties?(eg.?integrity,?molecular?mass?or?structure,?mechanical?strength)?and/or?by?fragmentation.?Note:?degradation?is?affected?by?environmental?conditions?and?proceeds?over?a?period?of?time?comprising?one?or?more?steps.?(Reference:?ISO?16929,?section?3.2)?

Compost:?solid?mature?product?resulting?from?composting?(Reference:?CAN/BNQ?0413-200)?

Composting:?managed?process?of?bio-oxidation?of?a?solid?heterogeneous?organic?substrate?including?a?thermophilic?phase.?(Reference:?CAN/BNQ?0413-200)?

Compostable?plastic?bags?and?compostable?products?must?be?compatible?with?the?dynamics?invo*ed?in?the?composting?process?and?not?detract?from?the?physical?and?chemical?quality?of?the?end?product,?compost.?

In?Canada,?for?a?plastic?bag?or?other?product?to?claim?compostable,?it?must:

??★disintegrate?by?at?least?90%?within?84?days?of?the?composting?process?

??★biodegrade?by?at?least?90%?within?180?days?of?the?composting?process?

??★have?no?ecotoxicological?effect?greater?than?10%?on?the?germination?rate?of?seeds?and?

??★vegetation?biomass?rate?

CRITERIA-?Background

The?process?to?establish?the?Canadian?criteria?for?the?evaluation?of?claims?for?compostable?plastic?bags?originated?because?of?plastic?bags?being?introduced?into?the?Canadian?marketplace?using?compostable?claims?that?were?not?valid?(ie.?they?were?not?compostable).

Originally?initiated?for?Québec?purposes?by?Recyc-Québec?and?the?City?of?Montréal,?the?development?of?the?Canadian?Certification?Program?for?compostable?plastic?bags?was?expanded?nationally?by?The?Composting?Council?of?Canada?with?support?from?the?provincial?ministries?of?environment?of?New?Brunswick,?Prince?Edward?Island,?Nova?Scotia,?Manitoba?and?Alberta.

The?Bureau?de?normalisation?du?Québec?(BNQ),?having?had?past?experience?in?standard-setting?for?the?composting?industry,?was?commissioned?to?coordinate?the?review?process.

Rather?than?re-inventing?the?wheel,?the?review?process?invo*ed?the?examination?of?existing?international?standards?for?compostable?plastic?bags?and?evaluating?their?appropriateness?for?Canadian?conditions?as?well?as?composting?facility?operational?and?product?marketing?requirements.

A?15-person?review?panel?was?selected?invo*ing?representatives?from?municipalities,?composting?facilities,?product?suppliers?and?users?as?well?as?consumer?groups.?Following?extensive?discussion?as?well?as?public?consultation,?the?Canadian?Certification?Program?became?official?in?September?2007.

In?2010?the?certification?program?was?expanded?to?include?compostable?products?of?all?types,?following?the?adoption?of?the?standard?CAN/BNQ?0017-988.?This?serves?to?adopt?the?standard?ISO?17088?as?the?national?standard?for?Canada.?It?is?important?to?note?that?the?original?program?for?the?certification?of?compostable?plastic?bags?(BNQ?9011-911/2007)?will?soon?be?cancelled?to?be?replaced?entirely?by?the?certification?program?for?compostable?products?(CAN/BNQ?0017-988).

Time?and?rate?of?degradation?and?disintegration?were?amongst?the?criteria?established.?Requirements?for?the?bags'?impact?on?the?finished?compost?from?the?perspective?of?visual?quality?as?well?as?trace?element?content?and?plant?exotoxicity?have?also?been?established.?The?final?set?of?criteria?selected?reflects?the?operational?and?regulatory?realities?which?composting?facilities?must?adhere?to?in?Canada?for?both?organic?residuals?processing?and?finished?compost?product?sale.

Those?manufacturers/product?representatives?wishing?to?adhere?to?the?Canadian?Certification?Program?and?use?the?compostable?mark?of?conformity?on?their?compostable?plastic?bags?must?submit?an?application?to?the?BNQ?for?review?and?meet?the?requirements?of?the?program.

Two?review?options?are?available:?

·?Submit?existing?compostability?test?results?from?internationally-
recognized?laboratory?organizations.?These?will?be?reviewed?by?the?BNQ?to?confirm?adherence?to?the?Canadian?Certification?Program.?

·?request?the?BNQ?to?conduct?the?testing?in?internationally-recognized?laboratory?organizations?of?the?selected?product?according?to?the?criteria?set?out?in?the?Canadian?Certification?Program.?

Both?options?have?costs?associated?with?them.?The?manufacturer/product?representative?should?contact?the?BNQ?directly?for?further?details.

Documentation
Copies?of?the?certification?program?documents?for?compostable?plastic?bags?BNQ?9011-911/2007?and?for?compostable?products?CAN/BNQ?0017-088?and?the?certification?protocol?BNQ?0017-988?associated?with??these?programs?can?be?ordered?directly?on?the?BNQ?website.

ABOUT?COMPOSTING

What?is?Composting?
Composting?is?a?natural?process?whereby?micro-organisms?transform?organic?waste?materials?into?a?soil-?like?product?called?humus?(pronounced?"hue-mous").?Kitchen?scraps,?leaves?and?yard?waste,?paper,?wood,?food-processing?wastes,?as?well?as?agricultural?crop?wastes?and?animal?manures,?are?excellent?organic?waste?materials?that?can?be?composted.

Composting?has?a?wide?range?of?benefits:?it?helps?to?reduce?the?amount?of?waste?going?to?landfills?and?produces?a?valuable?product,?compost,?of?benefit?to?soil?health?&?vitality?in?addition?to?many?other?attributes?such?as?water?and?soil?conservation.?It?is?estimated?that?about?40?to?60?percent?of?the?total?waste?stream?could?be?composted!

For?the?composting?process?to?work?best,?it?is?important?that?the?micro-organisms?have?a?continuous?supply?of?food?(i.e.,?organic?wastes),?water?and?oxygen.?As?well,?managing?the?temperature?of?the?composting?material?is?important?to?make?the?process?work.

Although?most?organic?wastes?supply?all?of?the?nutrients?necessary?for?the?micro-organisms?to?grow,?they?grow?best?with?certain?levels?of?carbon?(C)?and?nitrogen?(N).?Paper,?leaves?and?wood?are?high?in?carbon,?while?grass?clippings?and?vegetable?trimmings?are?high?in?nitrogen.?The?materials?in?the?composting?"recipe"?need?to?be?mixed?in?the?correct?combination?to?create?the?right?C:N?ratio.

Types?of?Composting
Composting?can?be?done?in?many?different?ways.?Types?of?composting?range?from?residential?or?backyard?composting?to?mid-scale?and?central?municipal?or?industrial?composting?systems.?Selecting?the?most?suitable?method?depends?on?the?amount?and?type?of?organic?materials?to?be?composted.?

Residential?or?backyard?composting?means?that?an?individual?household?composts?most?of?its?food?and?yard?waste?in?a?container?located?outside?the?home.?Worm?composting?is?a?viable?option?to?compost?kitchen?waste?indoors.?Composting?at?home?is?the?simplest?and?most?cost-effective?method?because?collection,?transportation?and?costs?are?avoided.?People?benefit?directly?from?their?own?efforts?by?producing?a?valuable?additive?for?their?own?garden?soil.?

However,?not?all?food?and?yard?waste?can?be?managed?so?simply.?Organic?material?from?commercial?sources,?such?as?restaurants,?supermarkets,?apartment?buildings?and?food?manufacturers,?needs?to?be?managed?differently.?This?is?where?mid-scale?and?centralized?composting?fits?in.?

Both?mid-scale?and?centralized?composting?invo*es?significantly?larger?quantities?and?a?larger?variety?of?organic?wastes.

Mid-scale?composting?is?the?on-site?management?of?organic?waste?generated?by?a?group?of?people,?such?as?in?an?apartment?complex,?office?building?or?hospital.?This?avoids?the?transportation?of?organic?waste.?Centralized?composting?invo*es?the?collection?and?transportation?of?organic?materials?to?a?special?facility?where?it?will?be?prepared?and?processed?into?compost.

Centralized?Composting?Facilities
The?design?and?set-up?of?a?centralized?composting?site?must?take?into?account?such?factors?as?the?type?and?volume?of?organic?waste,?waste?collection?methods,?sorting,?storage?factors?and?the?end?use?for?the?finished?compost.?Quality?organic?waste?and?good?operating?procedures?ensure?the?production?of?high-quality?compost.

Among?the?most?common?centralized?composting?process?technologies,?in?order?of?increased?technology,?are:

Windrows
Organic?materials?are?placed?in?long?triangular?rows?called?windrows.?Windrows?are?turned?and?watered?occasionally?to?ensure?that?the?micro-organisms?get?an?adequate?supply?of?oxygen?and?that?any?clumps?of?organic?material?are?broken?up.

This?method?is?commonly?used?for?composting?leaf?and?yard?waste,?commercial?food?wastes,?or?such?"specialty?items"?as?shredded?Christmas?trees.?

Static?Aerated?Pile
Organic?waste?materials?are?formed?into?windrows?over?perforated?pipes.?Rather?than?the?windrows?being?turned,?air?is?supplied?to?the?micro-organisms?through?the?pipes.?

Almost?all?municipalities?own?the?necessary?equipment?required?for?centralized?composting?operations?using?windrows?or?static?aerated?piles.?This?means?that?the?capital?costs?are?relatively?low.

In-Vessel
In-vessel?systems?are?either?fully?or?partially?enclosed,?and?can?handle?more?material?in?a?smaller?space?than?windrows?or?static?aerated?piles.?However,?they?tend?to?be?more?costly.?These?systems?provide?better?control?of?aeration,?temperature?and?the?moisture?in?the?organic?materials?being?composted,?all?of?which?result?in?faster?decomposition.

If?necessary,?water?can?be?added?to?maintain?the?correct?moisture?level,?and?air?can?be?pumped?in?to?provide?oxygen?and?to?control?the?temperature.?

Although?different?in-vessel?systems?are?available,?they?are?generally?of?three?basic?types:?channels?or?troughs,?containers?and?rotating?drums?(sometimes?called?tube?digesters).

Channels?(or?Troughs)
The?composting?process?takes?place?in?long?rectangular?troughs?or?channels.?The?organic?waste?materials?are?mixed?so?that?the?clumps?are?broken?up?and?the?material?is?aerated.

Containers
Composting?takes?place?in?closed?containers?that?are?supplied?with?air.?Excess?moisture?and?exhaust?air?are?removed?from?the?containers?to?maintain?ideal?conditions?for?the?micro-organisms?throughout?the?process.

Rotating?Drums?(Tube?Digesters)
Organic?waste?materials?are?added?to?a?drum?which?is?continuously?rotating.?The?rotation?ensures?that?the?micro-organisms?are?constantly?supplied?with?the?oxygen?they?need?and?that?all?of?the?organic?waste?materials?are?exposed?to?them.?The?material?remains?in?the?drum?for?three?to?five?days?and?is?then?transferred?to?windrows?for?final?curing.

Anaerobic?Digesters
Organic?waste?materials?can?also?be?digested?in?an?oxygen-free,?or?anaerobic,?environment?by?micro-organisms?that?do?not?need?oxygen.?The?length?of?time?required?to?digest?the?organic?waste?material?varies?according?to?the?individual?technology?usually?between?two?and?twenty?days.?The?process?produces?humus,?methane?and?carbon?dioxide.?The?methane?is?captured?and?converted?into?energy.?Following?digestion,?the?humus?can?be?transferred?to?windrows?or?another?method?for?final?composting.

Excerpts?from?Centralized?Composting?Helping?To?Complete?The?Carbon?Cycle,?written?by?Susan?Antler?of?The?Composting?Council?of?Canada?on?behalf?of?Environment?Canada.