Anaerobic Digestion Energy – Gaining Value from Biogas Energy Content

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Anaerobic Digestion Energy the sustainable renewable energy production process, is on an upward trend. The establishment of anaerobic digestion (AD) systems has accelerated substantially in the past several years. And, one area of growth is for livestock manure stabilisation and the associated energy production.

There are thousands of digesters operating at commercial livestock facilities in Europe, United States, Asia and elsewhere. which are generating clean energy and fuel. Many of the projects that generate electricity also capture waste heat for various in-house requirements.

The first anaerobic digestion (AD) facility was in operation in the mid-1800s in India. But, the technology fell into disuse while there was plentiful cheap oil.

However, it has seen a renaissance in most recent times, and the country with the best record of working with the technology is Denmark. That country by 2000, had introduced an energy production initiative that saw biogas levels rise rapidly, and they doubled in just a few years. Their lead was, within a few years, surpassed by Germany with close to 3,000 AD plants now operating.

Now, many other countries have government plans established and similar rapid rises in biogas production are expected.

Energy from Renewable Sources Anaerobic Digestion is Growing

There are more than 111 digesters operating at commercial livestock facilities in the United States which generated around 215 million kWh equivalent of usable energy. Besides generating electricity (170 million kWh), biogas is used as boiler and domestic fuel.

In 2015, for the first time the value of energy generated in the UK by renewable resources was greater than that of energy produced by UK oil and gas resources. Increased electricity generated from renewable sources between 2014 and 2015 (26%) contributed to the increase in value between this period (UK Office of National Statistics).

Municipal Wastewater Treatment Achieves Surplus Anaerobic Digestion Energy Production

Municipalities, like the East Bay Municipal Utility District in Northern California, realized that in the course of treating wastewater from households, farms and food processing facilities, they could add a step to produce some of their own energy.

For EBMUD, the last 15 years have been a journey in search of greater biogas to energy efficiency and energy production capacity. Waste treatment is an energy intensive process, and with the installation of 11 anaerobic digestion units and three turbines, EBMUD now produces 135 percent of its energy needs, leaving additional power that can then be sold, says Jackie Zipkin, manager of wastewater engineering there. via

Biogas Production Moves Away from Using Energy from Crops

A digester which produces anaerobic digestion energy (biogas energy)
Deer Island WasteWater Treatment Works Digester and Wind Turbine – CC BY by aismist

Almost any biomass can be processed by AD including food waste, energy crops, crop residues, slurry and manure. Cereals and rape meal can be used as AD feedstocks, giving high biogas yields, but are generally expensive. Dedicated energy crops with high biomass such as maize, can be grown specifically for anaerobic digestion.

However, it is recognised by most governments, including by EU policymakers, that using food crops for energy production might cause food prices to rise. Policies have been developed which avoid providing significant incentives to the use of food crops for energy in the last five or so years, use of food crops is likely to remain at a low level globally, so rise in food prices due to biogas production is no longer likely to occur.

Anaerobic Digestion in Landfills Produces Biogas which Can Easily Escape

Landfills are large contributors to carbon emissions as methane which is far more damaging as a greenhouse gas than the same volume of carbon dioxide. That means that it should always be collected and burnt in flares at the very least. But, much better is to clean the landfill gas and use it to generate electricity, or use it as a fuel equivalent to natural gas (but renewable).

Many governments now require landfill gas (biogas) to be collected and flared, or used for its energy value. There are several compliance options, including flaring the gas or installing a landfill gas use system.

Once the investment is made to use the energy, “landfill gas energy recovery” gives communities and landfill owners the opportunity to reduce the costs associated with regulatory compliance. They do it by turning polluting emissions into a valuable community resource. It’s a true win-win situation.

Image text: "Anaerobic digestion energy - Gaining value from energy content".

Energy Generation

The question is, which businesses are suitable for installing biogas to energy facilities?

The primary beneficiaries will be small farms and smallholdings which produce a lot of organic waste.

Most small-scale factories such as tanneries, textile bleaching and dying, dairy, slaughterhouses etc.,  discharging to public sewers may also be suitable for biogas to energy projects. However, many find it hard to afford effluent treatment plants of their own because of economies of scale in pollution abatement.

Biogas to Energy Advantages

Converting organic matter into methane in biogas to energy projects has many advantages. Recycling/ recovery/ re-use of products from the wastes of even small-scale units by adopting suitable technology is becoming a viable proposition, especially for the larger producers.

That’s one area where generation of energy using biogas to energy processes have proved to be economically attractive in many such cases.

The urban municipal waste (both solid and liquid) such as industrial waste coming from dairies, distilleries, tanneries, pulp and paper, and food processing industries, etc., is being used to make energy through this process.

Plus, agricultural waste and biomass is used as AD plant feed in different forms.

If treated properly, the anaerobic digestion process has a tremendous potential for energy generation.

Re-using Organic Waste Through the Production of Renewable Energy

Communities across the world are managing their waste with less impact on watercourses, while reducing odour. They are beneficially re-using their organic waste through the production of renewable energy, plus improving soils, with AD plant reactor residue output sourced mulches and natural fertilisers.

Where are the Valuable Sources of Biogas Energy Content?

Farms and ranches are common places where anaerobic digestion of waste materials can make sense.  There are typically large quantities of organic material available. This is valuable biogas energy content.

Digesters can effectively eliminate the environmental hazards of dairy farms and other animal stock rearing businesses.

The environmental reasons to start a biogas plant project, typically motivate farmers more often than the digester’s electrical or thermal energy generation potential does.

Other potential common AD facility uses are zoos or any facility located near a continuous source of biomass such as a contained animal feeding operation.

Biogas Energy Solutions – An Example Biogas Case Study in Quebec

Laflamme Waste-to-Energy has proposed a biogas to energy solution to two problems, those being waste management and energy generation.

  • Adding an integrated anaerobic waste treatment process to all sewage works, is an interesting option. But because of high investment cost and low energy value in the province of Quebec, it is hard for a municipality to commit to that solution.
  • A recent scientific paper investigated the economic possibilities to manage organic material, organic fraction of municipal solid waste, and municipal wastewater sludge by anaerobic digestion for a 150,000 inhabitant municipality.
  • Consideration also was given to achieving significant energy generation and greenhouse gas emission reduction. It was found that using the biogas to co-generation solution in that project would bring a payback time on investment (PBT) of 3.7 years.
  • This was based upon an electricity price at 0.10 $Cdn/kW h.
  • The addition of manure from surrounding farms would be proposed and if done well would be likely to increase the biogas production by 37%.
  • But, regulatory controls imposed when importation takes places were found to increase the PBT to 6.8 years. That is, unless the leftover digestate can be used as a saleable commodity, when it becomes an economically advantageous natural fertiliser product. via

While Quebec may find the economic benefits marginal without regulatory assistance in some form to allow the sale of the output as a fertiliser, elsewhere the arguments in favour of biogas energy are winning out.

As more biogas plants are built the science will advance and the biogas energy advantages will continue to rise.

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