Although this excerpt is rather long it is a great an in-depth look at biogas from alage. Tom Freyberg takes a deep look at the European funded All-Gas project that aims to treat wastewater solids with a combination of anaerobic digestion and algae to produce liquid biofuels in addition to biogas. In fact, this is only an excerpt so when yo get interested you will need to follow the link at the bottom of the artilcle to read the oiginal version. When you have read this do you thin that you could please give us your views on this suject. Yes. Please give us your comments!
First generation biofuels from crops never really bloomed into a fruitful harvest. Opponents criticized using up valuable land to grow crops and fuel the cars of the rich, instead of filling the stomachs of the poor. Second generation biofuels ? made from biomass - have proved harder to extract the required fuel and fully crack.And then along came algae. Unlike first generation biofuels, algae can be grown using land and water not suitable for plant and food production. Consuming solar energy and reproducing itself, algae generates a type of oil that has a similar molecular structure to petroleum products produced today. As if this wasn't enough ? algae growth also consumes carbon dioxide, a known major greenhouse gas (GHG).
As a result of the apparent benefits the race is on to commercialize second generation biofuels from algae. Continents and companies are putting money where their mouths are to find out how what we thought was simply a green weed growing in the sea could be the answer to inevitable fossil fuel shortages.
Earlier this year U.S. President Barack Obama announced that the Department of Energy would make $14 million of finance available to support research and development into biofuels from algae. The DoE has suggested that up to 17% of the oil imported for transport could be replaced with biofuels derived from algae.
Meanwhile Europe is going even further and mandating the gradual replacement of fossil fuels with biofuels. An EU Directive stipulates that by 2020 a total of 20% of energy needs should be produced by renewable fuels.
Even UK government backed agency The Carbon Trust has forecast that globally, by 2030 algae-based biofuels could replace more than 70 billion litres of fossil fuels every year - equivalent to 12% of annual global jet fuel, or 6% of road transport diesel.
So far, so good then. Yet while algae derived biofuels sound like an answer to inevitable fossil fuel shortages, two challenges remain: space and nutrients.
Phosphorous and ammonia are required alongside sun light and carbon dioxide to "feed" the algae. It is in response to this particular challenge where the wastewater sector could play its part, with untreated effluent being a known source of phosphorous and other nutrients. An EU funded project aims to bring together the challenge and solution and link the water and biofuel industries together.
The ?12 million, five-year project is starting at water company aqualia's wastewater treatment plant in Chiclana, Southern Spain and is backed by the European Union as part of its FP7 program ? supporting energy-related projects - with six partners.
Called All-Gas, which translates into algae in Spanish, the project will see "algal culture ponds" being used to grow micro-algae using nutrients contained in wastewater, such as phosphorous. A 10-hectare site will eventually be needed for the project.
Taking advantage of a warm climate, the algae grows using natural sunlight, before being processed for the extraction of oils and other valuable by products.
Frank Rogalla, head of R&D at aqualia, says that at existing algae farms, up to 30% of operation costs are normally the expense of buying and adding in nutrients to help with the algae growth. These nutrients are abundant in wastewater, he adds, so it makes sense to incorporate the two industries.
Traditionally aeration processes at wastewater treatment plants are heavy energy users, accounting for up to 30% of a facility's operating costs. In the U.S., according to the Environmental Protection Agency, drinking water and wastewater systems account for between 3% and 4% of national energy consumption alone.
He said: "We have converted our treatment to anaeraobic pre-treatment, meaning we will generate biogas from the start instead of destroying organic matter, so no aeration will be needed. From the 0.5 kWh [kilowatt-hour] per m3 which you generally spend for aeration, that will be completely gone. We will have a net output of energy from algae conversion either to oils or to gas. So that's why you get this positive output of 0.4 kWh per m3 of wastewater treated."
So the question has to be asked of how, technically, can the proposed treatment eliminate the need for wastewater aeration? The answer, as Rogalla later tells WMW, is through the initial conversion to biogas.
Compared to nitrification and dentrification to eliminate nutrients in conventional wastewater treatment, a process Rogalla says consumers about 5kwh/kg Nitrogen during aeration, All-Gas will use an alternative conversion. Firstly anaerobic pre-treatment will convert most organic matter into biogas (CH4 and CH2). Algae will then take up the nitrogen and phosphorous.
As the algae will transform most nutrients into biomass, they will also produce O2 in the process, as CO2 is taken up and oxygen released in their metabolic process. As a result, Rogalla says no aeration is necessary. Most organic carbon is transformed into energy (via biogas), nutrients are incorporated into algae, which produce oxygen for any polishing action necessary.
"It only seems logical to use the wastewater nutrients to grow algae biomass; on the one hand saving the aeration energy, on the other hand the algae fertilizer and cleaning wastewater without the occurrence of useless sludge, but producing biofuels and added value instead," Rogalla adds.
Space challengesAddressing the second challenge of space requirements to harness algae ponds, for a commercial scale operation it's estimated that a 10 hectare site is required (roughly 10 football pitches). But when compared to the oil yields of other crops, algae still proves favourable.
Data from U.S. based National Renewable Energy Laboratory (NREL) show that the oil yields in litres/hectare/year for soybeans are 400, which compares to 6000 for palm oil and a minimum of 60,000 for microalgae.
As predictions go, the production of 60,000 litres of biofuel from only one hectare of algae is optimistic in comparison to aqualia's aims for the Europe project. If a target set by the EU for the algae demo projects is reached, then each hectare should produce 20,000 litres of biodiesel. This, the firm says, compares to 5000 litres of biofuel per hectare per year for biofuels such as alcohol from sugar cane or biodiesel from palm oil. The Spanish project also hopes to use produced biogas from the anaerobic pre-treatment and raw wastewater organic matter.
One further benefit that has made algae growth attractive compared to other fuels is its consumption of Greenhouse Gases (GHG), namely CO2 in order to grow. It has the potential to reduce GHG emissions by consuming CO2 before it leaves the exhaust stacks from sources as power and cement plants. While the captured carbon will be released later when used in cars, it could still be a step in the right direction in reducing the impact of a world still firmly grasping CO2 emitting fuel sources.
The pivotal outcome of the project will be cost. This was proved in the well documented closure of the U.S. Department of Energy's algae research programme in 1996 after nearly 20 years of work. At the time it was estimated that the $40-60/bbl cost of producing algal oil just couldn't compete with petroleum at $20/bbl for the foreseeable future.All-Gas has the chance to spearhead Europe into proving that algae biofuel, through the help of wastewater, could be more competitive on a per barrel price with traditional oil
Tom Freyberg is chief editor of Waste Management World. email: tomf@pennwell.com
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