Carbon Neutral Biomass?

Until about 2008 it was often quoted that biomass fuels were carbon neutral. Extensive research was undertaken into harvesting, processing and transportation of biomass fuel from the place of production to the location of utilisation. It was found that many aspects of the supply chain were producing huge amounts of carbon.

Due to increases in demand millions of tonnes of biomass fuel pellets are now transported worldwide. The carbon production of transport must be taken into account when identifying carbon neutral status.

At SEEN we believe in local harvesting and production of biomass fuel from a diverse range of available sources. A few examples are listed below:

  1. Forestry and arboriculture waste products
  2. Clean timber including joinery off-cuts and construction site waste
  3. Used livestock and animal bedding
  4. Grasses including straw and other agricultural by-products
  5. Damaged livestock feed not suitable for animal consumption
  6. Food production waste such as seed pods and husks
  7. Bakery and confectionery production waste
  8. Food waste from domestic and commercial kitchens
  9. Brewery waste such as hop mash and brewers grains etc.
  10. Sewage treatment waste
  11. Paper and cardboard not suitable for recycling

There are many thousands of tonnes of waste available in Staffordshire which could be made into carbon neutral biomass fuel for private, commercial and district heating and hot water schemes, instead of going to landfill.

Timber and joinery waste, forestry and arboriculture waste can be readily processed into valuable biomass fuel for stoves and boilers.

biomass briquettes

Biomass briquettes manufactured from a range of materials

Thousands of tonnes of food waste is sent to landfill causing further environmental issues for future generations.

Waste food for biomass NOT landfill

Waste food for biomass NOT landfill

Organic waste can be treated by autoclave to sterilise the waste and prepare for conversion to biomass pellets or briquettes. The autoclave operates at 120˚C to 130˚C and the pressure can reduce bulk density by up to 80%. The autoclave waste solid fraction can then be processes into biomass pellets or briquettes for use in heating and hot water boilers.

There is a large volume of liquid output from the autoclave process, rich in sugars, amino acids and fats. This can be processed via anaerobic digestion [AD] to recover the energy. The 10% or so solid fraction from AD can be processed into biomass fuel.

The picture below shows Refuse Derived Fuel [RDF] manufactured from mixed food waste and packaging. At SEEN we want to work with waste producers to reduce contamination of food waste with packaging as the recovery of organic material from general refuse is made more difficult once everything is mixed together.

Biomass pellets manufactured from food waste

Biomass pellets manufactured from mixed waste [RDF]

Biomass fuel with 10% or less packaging can be used in DEFRA registered boilers.

Biomass pellets made from food waste

Biomass pellets made from food waste

The following tables give details of publicly available waste and recycling data extracted from Staffordshire County Council Annual Monitoring Report 2012/2013.

Table   4:   Estimated Controlled Waste Arising’s in Staffordshire and Stoke-on-Trent

Waste   Stream

Staffordshire

Stoke-on-Trent

Municipal     [1]

410,000

114,000

Commercial     & Industrial [2]

1,200,000

414,000

Construction,     Demolition & Excavation [3]

1,483,000

356,000

Agricultural     [4]

10,000

Hazardous     [5]

88,000

26,000

Total

3,181,000

910,000

1.   2012/13   Waste Data Flow Returns (DEFRA)

2.   2006/7   C&I Waste Survey (ADAS)

3.   2009   Update West Midlands Landfill Capacity Study (Scott Wilson)

4.   2003   Agricultural waste estimates (EA) apportioned by Staffordshire’s     contribution to the 1998 regional total of controlled waste. Figures     available for Staffordshire and Stoke-on-Trent combined only.

5.   2008   Hazardous Waste Interrogator (EA)

Table   5:   Municipal Waste Management 2012/13

Waste     Management Type Tonnes

Staffordshire

Stoke-on-Trent

curb side     & Recycling Centres

9,389,618

132,373

Composting     curb side and Recycling Centres

10,356,280

133,283

Energy   from   Waste

9,361,018

5,251,510

Landfill

88,380

10,222

Household     Waste

391,743

100,454

Commercial     Waste, Fly Tipping, Healthcare,

186,534

152,813

Soil   & Rubble   via Recycling Centres

122,883

33,721

 

Approximately 2 tonnes of food waste will produce almost 1 tonne of biomass after autoclave and completion of the pellet production process.

The table below gives comparison of calorific value and bulk densities of a range of possible fuel materials

Fuel

Net   Calorific Value (CV) by mass

Net   Calorific Value (CV) by mass

Bulk   density

Energy   density by volume

Energy   density by volume

GJ/tonne

kWh/kg

kg/m3

MJ/m3

kWh/m3

Wood chips

12.5

3.5

250

3,100

870

(30% Moisture   Content [MC])

Log wood

14.7

4.1

350
500

5,200
7,400

1,400
2,000

(stacked – air dry:   20% MC)

Wood

19

5.3

400
600

7,600   11,400

2,100
3,200

(solid – oven dry)

Wood pellets

17

4.8

650

11,000

3,100

Miscanthus

13

3.6

140
180

1,800
2,300

500
650

(bale – 25% MC)

House coal

27
31

7.5
8.6

850

23,000   26,000

6,400
7,300

Anthracite

33

9.2

1,100

36,300

10,100

General   industrial waste

16.0

4.5

150

36,300

680

Heating oil

42.5

11.8

845

36,000

10,000

Hospital   waste

14.0

3.9

120

35,900

470

LPG

46.3

12.9

510

23,600

6,600

Meat   and bone

18.6

5.2

640

11,900

3,300

Municipal   solid waste

9.5

2.7

100

950

270

Natural gas (NTP)

38.1

10.6

0.9

35.2

9.8

Peat

15.0

4.2

160

2,400

670

Poultry litter

8.8

2.5

540

4,700

1,300

Refuse   derived fuel

18.5

5.2

150

2,800

780

Short   rotation coppice

18.6

5.2

300

5,600

1,600

Tyres

32.0

9

460

14,700

4,100

By utilising available waste in a better way we have more than enough available energy supplies to satisfy local demands for biomass making it the truly carbon neutral energy source. WE need to work on establishing reliable sources of waste materials which has been prepared with care to maximise available energy recovery.

SEEN improving your world without costing the earth

Have you SEEN what we’re doing with waste? It’s not rubbish

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