A year in green tech: energy from green gunk

I love to travel.  Our development of ways to quickly and physically interconnect people of different cultures stands as one of the great achievements of the human species.  Except traveling long distances, and especially across continents, requires fuel.  Fuel comes largely from large fossil deposits within the earth, that when burned produce carbon dioxide and other pollutants that cause harm to our quality of life.  My love of travel has environmental consequences that counteract the positive effect that inter-cultural connectivity can bring.  As we quickly move to electrify our vehicle fleet for local and interstate travel, we will still power long-distance travel (trains, planes, and large ships) with chemical fuels for the foreseeable future.  If we could find a way to produce this fuel using the pollutants we put into the biosphere in such a way as to continually reduce the net pollution, while still providing the energy, that would reverse the deleterious effects, and remove travel from the list of undesirable activities.

As a first attempt, we started to grow biofuels from plants.  You will not read about traditional biofuel production in this series, because it does not meet a relatively simple requirement for green technology: it takes more energy to produce the fuel than the fuel contains after the process.  This highly inefficient process comes with an additional concern.  When using food stock (such as corn, soy, or sugar cane) as the input to the biofuel process, we introduce demand into the marketplace and affect the price of commodities that supply our nutrition.  Using arable land to grow fuel takes away land from food production, increasing the prices of basic commodities, and potentially every grown food product.  Although we have seen some potential in using the waste products from food production (such as the leftover stalks from corn and cane), we still do not see the efficiencies that a green fuel should have.

The most promising opportunity comes from the cultivation of algae - and more specifically, micro algae.  Although research into algae produces some confusion over their assignment to a specific kingdom, algae essentially are water-based plants that use photosynthesis to produce energy from carbon dioxide and other nutrients.  In the food chain, algae provide nutrients for water-based animal micro-organisms that then provide nutrients to small fish and sea life, and so on.  The useful characteristic that algae have comes from their storage of energy as a lipid, or fat.  If we can extract these lipids, we can convert them to forms of oils that then power the engines of trains, planes, and ships.

Image by John MacNeill, commissioned by Solix Biofuels

Cultivating algae, extracting the oils, and converting them to useful forms takes a significant amount of work, and until recently, required chemical solvents to make the process even moderately efficient.  Furthermore, extraction required significant energy inputs to dry out the algae to ready it for production.  The resource and energy intensity significantly increased the cost, and made increasing the scale of production difficult.  Recent research has found ways to eliminate the drying and chemical processing steps, instead using a continuous process that relies on heat and pressure to accomplish the task.  Although this does not significantly lower the energy input, it does allow for the commercialization of the process.  The energy input to an industrial facility that produces biofuel from algae can then use solar or some other form of renewable energy to accomplish the task, and at large scales, with much higher efficiencies than traditional biofuels.

The great promise of biofuel production from algae comes from the tangential benefits associated with the process.  The water in which we grow the algae can come from freshwater or saltwater, but even more beneficially, from wastewater.  Our wastewater from municipal sources contains many basic nutrients that we need to survive, but which pollute our freshwater sources.  These nutrients, primarily nitrogen and phosphorus, feed the algae, and as we harvest the carbon-based oils, we can also extract the nitrogen and phosphorus.  An algae production facility as part of a sewage treatment plant or run-of-river operation could significantly reduce or even eliminate eutrophication, the destruction of saltwater ecosystems by freshwater pollution.  In addition, as with all photosynthetic processes, the production of energy in algae requires carbon dioxide as an input.  Placing the industrial facilities near and around urban environments would remove carbon dioxide at rates significantly faster than current urban systems.  Monetizing the carbon, nitrogen, and phosphorous extraction, along with increased economy of scale, will bring the price of algae biofuels in line with expected prices for fossil fuels.

Even with this environmentally beneficial method for producing biofuels that can power our planes, trains, and ships, we still need to work on ways to extract the energy without the burning that releases carbon dioxide into the environment.  We also must continue to make the conversion process more efficient so we get more miles out of each unit of energy input.  If we can crack those nuts, and produce biofuels on a large commercial scale, we will have found a component of the green energy future that will allow us to maintain physical contact across borders without damaging our environment in the process.

Resources:
US Department of Energy Bioenergy Technologies Office
Pacific Northwest National Laboratory
Arizona State University Biofuels Initiative