Biogas from Food Waste: By Numbers

Posted by Clare Burns on 10-Jun-2015 09:00:00

A summary of the key figures – financial and environmental – involved in the production of biogas from food waste via anaerobic digestion.

infographic-biogas-from-food-waste

Biogas is a methane-rich gas produced by a biological process called anaerobic digestion (AD) – the biodegradation of organic matter in the absence of oxygen.

Organic food waste that is uneconomic to reuse or recycle is a suitable feedstock for AD. The biogas produced is a fuel that can be used to generate renewable electrical and heat energy.

chp-biogas

Source: Consultant’s Guide to CHP, ENER-G

Biogas that can’t be used on-site can be upgraded to biomethane and injected into the national gas grid or compressed and used as transport fuel.

1 Nm3 biogas (97% methane) = 1.1 Nm3 natural gas = 1.1 litres of petrol

Sources:

Alternative Uses of Biogas Group Report

Baltic Biogas Bus

Basic Data on Biogas

Existing number of UK AD sites

(Data from http://www.biogas-info.co.uk/maps/index2.htm.)

“The Government made a commitment to work towards a ‘zero waste’ economy in the Coalition Programme for Government of May 2010, and to introduce measures to increase energy from waste through anaerobic digestion (AD) … It is not possible to give a definitive growth potential for AD. However … an estimated potential for AD deployment for heat and electricity could reach 3–5TWh by 2020.”

The National Non-Food Crops Centre

Food manufacturing waste in the UK

Almost 16 million tonnes of food waste in the UK per year comes from households and industry – 25% (3.92 Mt) comes from food and drink manufacturing, distribution and retail.

 

Total 15.28Mt

Energy Savings

To optimise energy savings, biogas from food waste should be used to fuel a Combined Heat and Power (CHP) unit to generate on-site electrical and heat energy.

Conventional energy generation efficiency = 52.5% (grid electricity + natural gas boilers)

CHP generation efficiency = 85%

Generated energy outputs can vary considerably with biogas composition.

For example: digesting 1 tonne of food waste with a biogas yield of 100m3/hr would generate 200 kWh of energy.

Typical biogas yields of various feedstocks:

 

biogas m3/tonne

Cheese waste

650

Skimmed milk, dry

600

Potato flakes

500

Bread waste

450

Brewery waste

120

Rich fats

120

Buttermilk

50

Waste management costs will be reduced:

  • Costs associated with transporting waste to landfill will be eliminated.

  • Some sites may be exempt from environmental permitting if their control of waste meets the required criteria.

Financial incentives

Feed-in Tariff (FiT) – guaranteed income for generated renewable electricity for 20 years.

Anaerobic digestion total installed capacity

Income (p/kWh)

<250kW

11.21

250kW – 500kW

10.37

>500kW

9.02

Electricity exported to the grid can receive a minimum 4.5p/kWh – it’s negotiable with the energy companies.

Renewable Heat Incentive (RHI) – fixed income for generated renewable heat for 20 years.

Biogas combustion thermal output capacity

Income (p/kWh)

<200kW

7.5

200kW – 600kW

5.9

>600kW

2.2

Biomethane injection to grid

7.5


Renewable Obligation Certificates (ROCs) – certificate for renewable electricity generation under licence.

An anaerobic digester is eligible for 2 ROCs/MWh – currently 9.6 p/kWh (until April 2015).

Carbon savings

Biogas CHP provides significant carbon savings.

  • Energy generation using biogas from food waste instead of fossil fuels will reduce greenhouse gas emissions because the carbon in the food waste has been derived from an organic source with a short carbon cycle.

  • The CHP’s CO2 emissions are not adding carbon to the environment.

Takeaways:

Things to think about:

  • Anaerobic digestion produces biogas from food waste and residues.

  • Biogas is used to produce renewable energy with a CHP unit.

  • CHP provides 30% energy savings over fossil fuels.

  • Take advantage of the tariffs and incentives for renewable energy.

  • Save energy and improve your carbon footprint.

Discover how your food waste can decrease your business’s energy bills, reduce your carbon footprint, and provide additional revenue streams – download our free eGuide: An Introduction to Biogas for the Energy Manager

An Introduction to Biogas for the Energy Manager

Topics: Anaerobic Digestion / Biogas, Food and Drink Manufacturing

Clare Burns

Clare Burns is a technical marketer with many years’ experience in the energy arena, as well as in fashion, telecoms and education. Fluent in 3 languages, Clare has worked across Europe. She currently works for ENER-G, a UK manufacturer of carbon reducing, energy efficient products exporting its cogeneration technology across the globe.