Ilse Reijs and Jan-Noud HuttenPatrick Williamson examines an exciting prospect in the world of alternative energy.

A current research project that is being conducted by the US American Aeronautics and Space Agency NASA has received significant media interest of late. The project, described in true NASA fashion by the Grecian acronym OMEGA, does not relate, as one might expect, to space travel, or indeed in any way to the extra-terrestrial. Instead the project seeks to address issues much closer to home. OMEGA stands for Offshore Membrane Enclosure for Growing Algae, and refers to a system devised to utilise algae contained in offshore tubes known as modules. These modules would simultaneously treat wastewater, sequester carbon dioxide emitted by nearby power stations and act as an alternative energy source by producing biomass which can be readily converted into biofuel. Biofuel is considered to be far removed from the Holy Grail of renewable resources. Its combustion produces greenhouse gases in a similar way to its fossil fuel counterparts and the crops traditionally used to generate biofuel are in competition with crops intended as food stuffs for agricultural land, fertilisers and fresh water. This has sparked the “food vs fuel” concern about the collapse of the food markets as a result of extensive crop cultivation for biofuel manufacturing. However, the OMEGA project intends to avoid some of these issues and attempts to counteract those it cannot prevent.

The key to the project lies in the fact that it is offshore. Algae are grown in a network of plastic tubes floating in the sea, thereby not competing for agricultural area on land. The sea also has other useful functions for the project, acting as a natural thermostat keeping the algae at a constant temperature in which they grow well. Constant agitation from waves is said to act as a form of mixer, ensuring that the algae and nutrients are well dispersed through the module (although NASA have admitted to aiding this process by means of a mechanical rotor). The OMEGA system does not compete with food crops for freshwater supplies as the system is only intended to be fed with wastewater; the nutrients contained therein being beneficial for algae growth. In this way the system is not only used to generate biofuels, but also acts as a wastewater treatment facility. When the nutrients have been used up, the freshwater simply diffuses out of the semipermeable plastic tubes into the ocean by the process of osmosis.

Like other plant species, algae require carbon dioxide to grow; incorporating the carbon into their structure whilst liberating oxygen as a by-product. NASA intends to use this fact to ensure that the OMEGA system serves another purpose. The OMEGA system is to be fed with flue gas from neighbouring power stations as a source of CO2. The algae can therefore be used to prevent carbon dioxide from power stations being emitted into the atmosphere, thereby offsetting (at least somewhat) the CO2 produced upon combustion of the resultant biofuel.

Despite these beneficial functions that the OMEGA project promises to perform, many environmentalists may still be wary, if not all together appalled, by the concept of plastic sacks of sewage and algae floating in the oceans. NASA’s response to such critics is as follows: the OMEGA system is comprised of a series of small, self-contained modules. This modular set-up is intended to ensure that ruptures would only concern small, localised portions of the system. Such ruptures would admittedly release waste water into the ocean environment. However, the USA estimate that 80% of wastewater produced globally is released into oceans without treatment. Therefore a ruptured module (an event which is hoped to be a rare occurrence) would merely release something into the sea which would be there anyway in the absence of OMEGA. Research is currently being conducted on using biodegradable plastic to house the algae, thereby ensuring no waste should remain in the ocean in the event of the loss of a module. As for concerns of an invasion of alien species on the marine habitat, NASA have selected a species of algae which grow rapidly in freshwater (as fresh as wastewater may be considered) whilst dying particularly quickly upon contact with saline water, where they biodegrade. In fact, NASA go one step further by claiming that the modules could in fact be considered beneficial to marine biodiversity by providing habitat for seaweed and molluscs.

It is uncertain how cost effective this method of manufacturing biofuel would be. NASA believes that in order to ensure the commercial viability of the OMEGA system as a means of producing fuel, the value added by the services provided by OMEGA, such as water treatment and CO2 sequestration, must also be taken to account. In this spirit NASA have drawn up what seems to be a somewhat utopian vision in which the OMEGA modules contain inbuilt wind turbines and tidal generators for the generation of renewable energy, whilst simultaneously offering space for aquaculture; for example in order to farm scallops as a food source. In a press-release a spokesperson for the project even showed photographs of a seal frolicking on the surface of an OMEGA module to emphasize the harmony between the system and the natural environment into which it is to be placed. Irrespective of the realism of such visions, it is hard not to see the potential of such a project in a time where fossil fuel reserves are known to be dwindling, unlike our dependence thereon, which seems, as ever, undiminished.

 

Patrick Williamson

 

Image by Ilse Reijs and Jan-Noud Hutten