Recycling & Co-Product Exploitation
Food Waste Collection
Considerable research has been carried out in the UK looking at the best methods to collect domestic food waste for recycling. The most common method has involved mixed collections of kitchen and garden waste, presumably driven by the logistical simplicity of having a single collection. The fact that the average household produces only about 3kg of food waste a week may also have been a driver against separate food waste collections. However, research (see reports below by Eunomia and ECT) indicates that separate food collections are actually more cost effective for councils. This is due to the fact that food waste must be treated in accordance with ABPR. Suitable methods can include Anaerobic Digestion (AD) and In Vessel Composting (IVC) but not the far cheaper option of open windrow composting. If kitchen and garden waste are collected together then all this material must comply with ABPR. This vastly increases the cost to dispose of garden waste which, if collected separately, could be processed much more cheaply by the open windrow method.
DEFRA comissioned a research project (run by Brook Lyndhurst) to look at consumer response to different methods of food waste collection in 6 local authority areas. This work showed that the majority of people participate in these schemes with uptake being highest with separate food waste collections (rather than mixed with garden). Alternate Weekly Collection of residual waste also increased participation in weekly food waste collections. Between Jan 07 and March 08 WRAP have supported 19 councils to conduct weekly food waste collection trials, to develop good practice guidance in the design and operation of food waste collection schemes.
If such schemes are rolled out on a nationwide basis it will require a vastly increased capacity of AD and IVC to process the food waste collected.
WRAP project reports:
Wasting Food and Insistent Behaviour
Helping Consumers Reduce Food & Vegetable Waste : Interim Report
Food Waste Report v2 - "The food we waste"
Down the Drain: Quantification and exploration of food and drink waste disposed of to the sewer by households in the UK, November 2009
Food Waste Collection Reports:
Separate Food Waste Collections
Consumer Views on Recycling Food Waste
Dealing with Food Waste (Eunomia)
Composting
Composting is the biological breakdown of biomass by microorganisms which occurs in the presence of air. The process generally takes up to 6 months (including the maturation phase) and gives up to a 50% reduction in quantity of material. The end products of composting are carbon dioxide and a solid organic fertilizer.
Composting provides possibly the simplest option for treatment of food waste and the composting industry is currently growing rapidly with the increase in separate collections of green and food waste.
Numerous technology suppliers exist in the UK who provide In Vessel
Composting systems including the following companies:
http://www.theteggroup.plc.uk/
http://www.quickcompost.co.uk/
http://www.vcutechnology.com/
http://www.hotrot.co.nz/UKEire/ukeirehome/
Methods
Moisture content is critical to successful composting and some food
waste can be wetter than ideal for composting and quite often is treated
as a mixture with green waste. Green waste helps to add structure
to the compost and aid aeration.
However, Food Waste must be processed by “In Vessel Composting
Systems” whereas green waste can be treated in open windrows.
This means that treating the 2 waste streams together results in considerably
higher costs for green waste treatment. As green waste is generally
obtained in far higher quantities than food waste considerable savings
can be achieved by separate collection and treatment. Systems
treating food waste must provide a sufficient processing temperature
to comply with the the most recent legislation in the UK 2005
Animal By-Products Regulations (ABPR) and the related EC
1774/2002 Regulations have led to significant changes in the allowed
use and treatment of animal by-products (ABPs).
Home Composting
An alternative process for treating domestic food waste is home composting
which has additional benefits of not incurring transport costs or emissions.
For this reason home composting, where possible, is a preferred treatment
method for domestic biodegradable waste. However, very simple
compost pile systems don’t consistently provide a high quality
product and if not adequately managed can develop into an anaerobic
system with the resulting methane emissions. Additionally
home composting is not recommended for treatment of meat and cooked
foods due to the potential risks of odour problems and attracting vermin.
Anaerobic Digestion
Technology
AD is similar to composting in that biodegradable materials are broken
down naturally by micro-organisms. However, the anaerobic process
generates a mixture of carbon dioxide and methane (known as biogas)
which can be used as a valuable source of renewable energy. There
is considerable variation in AD processes for example the process may
by classed mesophilic or thermophilic depending on the temperature at
which it operates. Thermophilic processes take place at about
55°C and proceed more rapidly than lower temperature mesohphilic
processes at about 35°C. Thermophilic processes can give higher
yields of biogas and result in a smaller footprint of plant. On
the negative side, the process can be less stable due to the limited
range of thermophilic microorganisms and also requires consider energy
input to maintain the temperature. Moisture content of the feedstock
can also affect the type of technology used with feedstocks of <15%
dry solids being classified as wet processes and those with between
15-40% dry solids as dry processes.
More information on varying AD technologies can be found at the following
links
http://www.anaerobic-digestion.com/html/environmental-benefits-of-anae.php
England's Official Information Portal on Anaerobic Digestion
REA Waste Protocol Development Documents
Use of technology and barriers to use:
In some ways AD is a more suitable technology for treatment of food
waste than composting as the high moisture content of food (usually
about 75%) make it a good composition for this technology. Food
is also a comparatively high energy feedstock and therefore results
in higher energy generation than other feedstocks such as animal manure.
However food waste does require a heat treatment stage in order to comply
with the animal byproducts regulations. This can be achieved within
the AD process if operating under thermophilic conditions (requires
57°C for 5h) but under mesophilic conditions requires a separate
treatment stage either pre or post digestion. To date although this
technology is well exploited in many European countries, very few AD
facilities are operational in the UK partly due to the comparatively
high cost involved in set up of these plants.
Existing facilities in the UK include the following:
Ludlow, Shropshire http://www.biogengreenfinch.co.uk/
Holsworthy Devon http://www.devon.gov.uk/renewable_energy_guide_case_study_2.pdf
A historical blocker to the exploitation of AD in the UK has been a lack of available outlets for the digestate product. While this material is classified as a waste finding sufficient outlets has been a problem. Work is currently underway to develop a quality protocol and standard (PAS 110) for digestate which would enable it to be reclassified as a fertiliser rather than a waste.
Incentives
Under the proposed reform of the Renewable Obligations Certificates
(ROCs) due to take effect from April 09 AD facilities should be eligible
for 2ROCs per MWh of electricity generated. This change is targeted
at encouraging the uptake of this technology and should make the economics
of proposed facilities look considerably more favourable.
Anaerobic Digestion Reports:
DEFRA Methane Management Report
DEFRA CAD in Dairy Chain Report
Certification Scheme for Quality Protocol and PAS110 (REA)
Case Studies
Biogas - from AD : Biogen UK - http://www.biogen.co.uk/food_waste/recyclable.asp - BIOGEN's integrated Anaerobic Digestion (IAD) plant is capable of treating the widest range of biodegradable wastes including liquids, slurries, abattoir and wetter waste. It offers food waste producers a flexible, local, waste solution with great green credentials and with pathogens destroyed as part of the process.
Article from July 2008 issue of Biogas Magazine - Biogas from AD at McCains- For food and beverage companies producing moist or liquid waste, anaerobic digestion (AD) offers a good solution for generating renewable fuel for CHP systems. AD employs microbes in an oxygen-free environment to break down organic waste into biogas. The biogas, composed of methane and carbon dioxide, feeds a reciprocating engine, microturbine or boiler to generate electricity and process heat.
Agrana Biogas
from AD - Austria-based Agrana, one of Central Europe’s leading
sugar and starch producers, recently installed a $10.5 million AD system
at its sugar refinery in Kaposvár, Hungary. The digester processes
spent beet pulp and beet syrup to produce almost 3.9 million cubic feet
of biogas a day. From the July 2008 Issue Biomass magazine
http://www.biomassmagazine.com
"Spent Grain from Royal Brewery Manchester" - extract from Biomass Magazine
UK - food and drink manufacturers prevent half a million tonnes pa of food waste
Provalor - "Making money from food industry by products" - Presentation
Proper de Mulder - "Animal By-Products Fuel a CHP system"
InSource Technology - "Anaerobic Digestion a win- win technology" - presentation
Biowaste2energy - Launch of Waste to Energy company - News Release, 1 Feb 2008.
FareShare Community Project Press Release
