Small scale anaerobic digestion is a wide ranging term, and can be taken as the description for all anaerobic digestion plants in sizes ranging from a single dwelling, up to a community digester. We think that most people would agree that large farm digesters in the developed nations would usually fall into the “large scale” category. But, in the area of “small-scale” there is scope for much wider use of anaerobic digestion. So, in this article we report upon a new type of smaller scale AD Plant that seems to be emerging.
New! Watch our video definition of Small-Scale Anaerobic Digestion below, if you have any doubt what these plants are:
We are featuring small-scale anaerobic digestion plants, installed at the back of supermarkets. These can be very environmentally sustainable, and may be hardly noticed by the public. To have one now operating in Portugal, with no doubt more to follow, is a big step forward for supermarket biogas production.
The new breed is biogas plants designed to digest the organic waste produced by a single supermarket on-site, at the back of the store. They are based upon container units which house the bio-reactor tank (or tanks), the biogas storage, and all the Mechanical & Electrical devices and electronic computer control systems.
This is a model for biogas energy production which can immediately be used to power the supermarket’s own energy needs (by electricity generation), and provides also an opportunity to use the CHP energy in cold weather. for space heating of the supermarket as well. Put that together with the absence of fossil-fuel consuming energy use in “transport miles”, for the organic waste to be taken to a biogas plant, and the availability of staff on-site to look after the digester itself and this must be a winning, and very highly “green”.
It is a green solution, because by reducing carbon emissions, climate change will be reduced and thus this is a sustainable solution to the problem of waste food from supermarkets.
The project we refer to is the first of its kind, and has been developed by SEaB Energy, as described in their Press Release below:
SEaB Energy deploys its ‘Power in a box’ technology at Portuguese supermarket leader Modelo Continente
SEaB Energy, one of the UK’s brightest innovators of waste to energy technology, has fully implemented its containerised power plant at a hypermarket owned by Portugal’s largest retailer. This is the first time that an anaerobic digestion system, that converts inedible food waste to energy, has been installed at a supermarket site anywhere in Portugal.
The strategic partnership agreement, signed with Modelo Continente, part of the Sonae Group, was conducted through SEaB Energy’s Portuguese agent, Biowaste SA. The conclusion of the deal has resulted in SEaB Energy’s ‘Flexibuster’ technology being installed at Continente’s hypermarket in Gaia, located in the south of Porto.
SEaB Energy’s patented ‘Power in a box’ small-scale power plant is now fully operational and will deliver an immediate revenue stream for Modelo Continente as well as having a significant positive environmental impact to the site.
Sandra Sassow, CEO of SEaB Energy commented:
“This is a ground breaking deal for the adoption of small-scale renewable energy systems within the retail sector – and not just for Portugal but for Europe as a whole. It also demonstrates Continente’s continued commitment to adopting sustainable solutions that also improve their operational performance and enhance their environmental credentials.”
The Flexibuster will convert approximately 600kg per day of inedible supermarket food waste into energy that will generate around 80,000Kwh of electricity, as well as 180 tonnes of digestate fertilizer per annum. The electricity will be used on site whilst the fertilizer will be sold on, creating another valuable revenue stream for the supermarket.
The total offset savings for the first year is projected to be around €27,000 which includes income from energy generation and cost savings from the elimination of waste transport and landfill costs as well as other operational expenses.
Modelo Continente is a pioneer in the adoption of low-carbon, environmentally-friendly measures that reduces its demand for energy and includes LED-only lighting in all new stores, installation of over 112 photovoltaic power plants and the use of more efficient heating and cooling equipment. The company also has a strong focus on resource recovery including the recycling of product and transport packaging and the implementation of bins at its stores so that consumers can recycle items such as batteries, clothing, consumables and electricals.
About SEaB Energy
SEaB Energy Limited is a UK company, designing and commercialising breakthrough product innovations which create clean energy and water from onsite organic waste.
All images are copyright with “All rights reserved” by SEaB Energy.
Other Small Scale Anaerobic Digestion Plants/ Installations
Small Scale Anaerobic Digestion isn’t by any mean just confined to supermarkets. In the sections which follow we discuss other small-scale AD installations.
On-Farm Micro-scale Anaerobic Digestion Plants
Micro-scale digestion involves the production of biogas, but on a small scale within farms. The small-scale digestion production units are below 80 kW. Most agricultural units have a power capacity between 100 and 300 kW, while some industrial units exceed 1,000 kWe. A small-scale digestion project is carried out starting from 100 dairy cows or 200 sows.
“The interest for small-scale digestion is not to have to invest in large facilities,” explains François Xavier Dumur, Novatech Project Manager. “Micro-scale digestion allows the autonomy of the system by supplying the digester with the farm products.” via biogasworld.com
The agricultural sector should see significant deployment of farm scale AD plants in the next decade. Digestate should be returned to land and it makes sense to site plants on or close to farms. AD can reduce odour emissions from livestock slurries and manures, plus nitrate and phosphate run-off from storage and spreading of undigested manures. But the digester must fit the farm.
Britain’s farm manures have a methane potential of 10bn kWh of thermal energy per year. But, if not digested, estimated GHG potential is 3m tonnes CO2 equivalent.
Hence, AD should be more widely adopted on livestock farms – with farm scale plants. Germany recognizes the value of AD for on-farm pollution control and nutrient recycling, with enhanced incentive payments for smaller on-farm slurry based digesters. via recyclingwasteworld.co.uk
Small-scale Biogas Reactors at Household or Community Level in Rural Areas
Small-scale biogas reactors are also often designed to produce biogas at the household or community level in rural areas. The airtight reactors are filled with animal manure from the farm. Kitchen and garden wastes can also be added and toilets can directly be linked to the reactor for co-treatment of excreta.
A biogas reactor is an airtight chamber that facilitates the anaerobic degradation of blackwater, sludge, and/or biodegradable waste (e.g. It also facilitates the collection of the biogas , a mixture of methane (CH4) and carbon dioxide (CO2) produced in the fermentation processes in the reactor. The gas forms in the slurry and collects at the top of the chamber, mixing the slurry as it rises. The pressure exerted by the rising gas can be used to transport the gas to the collection vessel or directly to where it is going to be used.
The digestate is rich in organics and nutrients, almost odourless and pathogens are partly inactivated. via sswm.info
AD is a multi-purpose process. Small-scale anaerobic digestion plants reduce the GHG emissions from the storage of the livestock manure. The recovered biogas replaces oil, kerosene or wood as fuels and in doing so reduces the release of particulates and toxins into the atmosphere.
As a consequence, their detrimental effects on human health are reduced, while the reduction or elimination of pathogens during the process can lead to improved human health as well as animal health and productivity.
These small scale anaerobic digestion plants wherever they are located can usually be integrated into a wholly sustainable farming system for the reduction of pollution to land, air and water. via iea-biogas.net