Biogas da Microalghe, Nord America

Biogas
 

With strict permitting conditions regulating odour emissions from anaerobic digestion facilities, and little government funding, the technology has been slow to take off in North America. Now however, by utilising algae to clean the biogas and capture valuable compounds such as Omega-3, one Canadian company claims to have the solution both problems.
 

by Ben Messenger

In many countries in Europe the use of anaerobic digestion (AD) facilities to produce biogas and fertiliser from agricultural, municipal and commercial organic wastes is well established. Backed by government subsidies and feed-in tariffs, anaerobic digestion has flourished in Germany, which has well over 6000 operating plants – 70% of them located on farms. Indeed so successful has the German biogas industry been that there have even been warnings of over-capacity and questions raised about the availability and suitability of feedstocks.

Other markets however have not been so quick on the uptake. Notably, North America, where with little government funding the entire continent currently has less than 200 AD facilities. Further hampering developers has been the lack of landfill diversion regulations for organic wastes, and often strict environmental regulations for air and water quality – particularly those relating to the release of odorous hydrogen sulphide – which has made obtaining permits lengthy and costly. Furthermore, as has been the case for other renewable technologies, the arrival of cheap and plentiful shale gas has done little to help the economics.

Due to these factors AD developers in North America rely heavily on tipping fees, with paybacks typically in the five to seven year range. With all the talk of the ‘fiscal cliff’, the prospect of North American countries providing the level of government funding which helped build Germany’s biogas industry seems unlikely. If AD is to become a more attractive prospect to investors in the region it will be necessary to increase the revenue generating potential for such facilities.

One company with a technology which it claims can do just that is Toronto, Canada based Solutions4CO2, which has developed what it calls the Integrated Biogas RefineryTM (IBR) platform. According to the company the system can reduce the payback for AD projects to less than three years with the production of high value Nutraceutical and Pharmaceutical co-products such as Omega-3 and Astaxanthin.

 

How it works

EPA biogas systems
According to the EPA biogas systems, such as the 100,000 TPA Fremont Community Digester pictured, are feasabile at 8000 swine and dairy farms in the U.S.

According to Dil Vashi, manager of corporate development at Solutions4CO2, at the heart of the system lays the company’s own proprietary Biogas Purifier and Infusion SystemTM (BPIS).

“What the BPIS does, is it essentially infuses and completely dissolves CO2 and Hydrogen Sulphide (H2S) into water because they are soluble gases. The methane (CH4), which isn’t soluble, passes through the water and flashes off. So what you end up with is the CO2 and H2S being captured in the water and the methane stream off gassing. You go from a biogas stream which is typically 60% methane, 39% CO2 and less than 1% H2S, to a biogas that is over 90% methane and the CO2 and H2S being reduced by 85% – 95%,” explains Vashi.

“The significance of our system is that when you grow algae in that CO2 and H2S infused water, it gives you an increase in your algae growth yield of over two to three times. What we do then, is we take that algae and we harvest it, dewater it, dry the biomass and then extract certain high value oils – primarily Omega-3 and Astaxanthin – and then sell them into the nutraceutical and pharmaceutical industries,” he continues.

To infuse the CO2 and H2S into the water, Vashi says that the company’s BPIS differs from more common fine bubble sparging techniques, which operate under pressure with very small bubbles, by displacing other molecules present in the water such as oxygen and nitrogen. Infusing the CO2 and H2S at a molecular level results in a bubble-less solution, which makes it considerably easier for the algae to consume the infused gases.

ACS units
The modular system can operate with as few as one or as many as 200 ACS units

Cultivated in an Algae Cultivation System (ACS) that is comprised of an LED lit tank, or photo bioreactor, the algae consumes the CO2 and H2S as a nutrient, and essentially processes them into high value compounds such as Omega-3 and other long chain carbon compounds. To harvest the algae, every couple of days around 50% of it is scooped from the top of the photo bioreactor by the Harvesting and Extraction System (HES), which dewaters and dries it, and then extracts the high value oil. The remaining 50% remains in the bioreactor as an inoculum to get the next batch of algae started.

According to the company its IBR is a closed loop system which utilises all of the outputs of the AD system as inputs to the co-product platform. Power, CO2, H2S, clean methane, water and digestate from the AD are utilised as inputs to the co-product platform, with all residual co-products sold to generate additional revenue. The resulting revenue enhancement effectively reduces project paybacks to less than three years.

 

Economics

 

In addition to allowing the cultivation of algae, another major advantage of purifying the methane is that it allows lower capital expenditure and maintenance costs for the generator set, as well as higher air quality standards for H2S – particularly significant in the North American market.

In terms of the extra running costs associated with the additional equipment at a facility with an installed IBR, Vashi cites the example of a typical AD plant producing around 300 cubic feet (8.5 cubic metres) of biogas per minute and generating around 6 million kWh of electricity each year. The power consumption of the IBR – the BPIS, the ACS and the HES – in total consume around 1 million kWh per year – with the AD’s parasitic load consuming around another 1 million kWh per year, leaving 4 million kWh per year for export to the grid.

BPIS
BPIS
The BPIS displaces other molecules in the water

But the real money spinner for the system is in the sale of the recovered high value co-products. According to food industry market research company, Packaged Facts, consumer spending on products fortified with Docosahexaenoic Acid (DHA) and Eicosapentaenoic Acid (EPA) from Omega-3 will grow from $25.4 billion in 2011 to $34.7 billion by 2016. Meanwhile the market for Astaxanthin – a natural nutritional component which can also be used as a food supplement and is considered an ‘E’ number in the European Union – is currently estimated at a more modest $60 million, but is expected to grow rapidly to $200 million by 2015.

While traditionally Omega-3 oil has been sourced from fish oil, interestingly, the fish themselves don’t actually produce Omega-3, it’s the algae they eat which produce it and it builds up in the bodies of the fish that typically cannot process it – which ours can.

The company is currently completing its first commercial IBR facility in Canada at an existing AD installation which processes a mixture of dairy waste and commercial food waste into biogas for power generation.

The IBR will be integrated with the AD and will process live biogas from the AD as an input for the IBR to produce algae biomass containing high value nutraceutical and pharmaceutical co-products.

Vashi adds that the IBR is modular and linearly scalable and can be built in scale from one to 20 or right up to 200 ACS units depending on the size of the AD and biogas production, and capital available to invest in a project.

Huge Potential

In making its case that the time has come for AD to flourish in North America, the company points to the 60,000+ dairy farms in the U.S. alone – 2000 of which exceed 1500 heads in size. At 1500 heads a dairy farm can sustain a digester capable of producing 300 cubic feet (8.5 cubic metres) of biogas per minute. According to the U.S. Environmental Protection Agency (EPA) biogas recovery systems are technically feasible at more than 8000 U.S. dairy and swine operations, and could generate some 13 million MWh of electricity each year.

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http://www.waste-management-world.com/articles/print/volume-14/issue-1/wmw-special-biowaste-focus/is-algae-the-answer-for-biogas-in-north-america.html

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