Microbes—the Future of Environmental Sustainability?
Green seems to be the new cool. People are reducing, reusing, and recycling more than ever. However, this may not be enough to protect our planet. Sustainability happens when resources are replenished at the same rate they are used. This is impossible while we use fossil fuel! Petroleum is a finite resource—with byproducts that are not in the least beneficial. World energy consumption is expected to increase by at least 40 percent over the next twenty years. A revolution in the way we obtain materials and utilized energy is not just a good idea, but is required. Where will this energy come from? How will we maintain our modern way of life and maintain ecological balance at the same time? Microorganisms might provide the answers.
The ability of microbes to evolve and adapt to their environment surpasses all other living species. For billions of years they have inhabited every corner of the Earth, efficiently converting a plethora of substances into energy and material for their own livelihood. Already a large portion of renewable fuel is produced with the help of microorganisms, and scientific research continues to show that microbes could provide a solution to the world’s future energy needs. And the benefits of bacteria don’t stop there. Bacteria and other microbes may have the ability to provide biodegradable plastic, clean up toxic waste, and contribute to sustainable agriculture. It is time we take full advantage of these amazing organisms.
Biofuel
It has long been known that microbes have the ability to produce ethanol—the alcohol in beer and wine—and that ethanol is an excellent fuel source. Ethanol is a byproduct of fermentation, which is the digestion of sugar with no oxygen present. Most of these sugars come from corn or other food crops. Fermentation is an ancient process; it is only natural for this to be a starting point in developing renewable energy sources. Ethanol is currently a common gasoline additive. Many people feel cheated at the pump if the gasoline contains 10 percent ethanol, but this combination makes gas burn cleaner and reduces the consumption of fossil fuels.
The United States became the world’s leading ethanol producer in 2006. Not surprisingly, many people are displeased with this fact. Production of ethanol from food crops has lately been the subject of controversy. This is because the corn used to produce ethanol could have fed people instead. At some point, an increase in the production of ethanol could also mean a decrease in the food supply. So far, this has only been a hypothetical issue because the production of corn has increased to match the demand. But, what about the future? There is simply not enough farmland to produce the amount of corn needed to keep up with the impending ethanol demand. This has driven scientists to research cost-effective ways to produce second-generation biofuels.
Biofuel is a broad term. It defines any fuel derived from or consisting of biomass (biological matter). Ethanol produced from microbial fermentation of corn is considered a first‑generation biofuel, but second-generation biofuels are being developed that convert non‑edible plant materials into ethanol. With the help of specialized bacteria, scientists hope to turn cellulose into fuel. Cellulose is the world’s most abundant biomass, but preparing it for fermentation, and as a result turning it into ethanol has proven to be a complicated process. Plant materials must be broken down mechanically or chemically to make the cellulose available for microbial fermentation. Scientists are currently exploring pretreatment options and are trying to discover or design the perfect microbe for the job. If they do, an abundance of readily available organic materials will be turned into ethanol—enough ethanol to meet future demand.
Biodiesel
Algae are another option on the path toward sustainable fuel. These fascinating microorganisms use sunlight and carbon dioxide, like plants, to produce their biomass. This highly efficient photosynthetic process also gives algae the energy they need to produce complex oils that help them float on the surface of water. These oils are full of hydrocarbons—the same type of molecules that make up petroleum diesel. Just like petroleum diesel, these hydrocarbons can be turned into gasoline. According to Yusuf Chisti in “Biodiesel from Microalgae,” “microalgae appear to be the only source of biodiesel that has the potential to completely displace fossil diesel.”
Production of algal biodiesel has the potential of being a waste free, even waste-reducing process. If algae grow in water from a water-treatment plant, consume carbon dioxide from power plant exhaust, and become animal feed after the oil-extraction process, this microbe could provide us with the most versatile and sustainable fuel production process yet. Unfortunately, many obstacles must be overcome before these ideas become a reality.
According to the International Energy Agency, the current cost of producing biodiesel from algae is relatively high. Companies and researchers are trying to figure out how to lower these costs. A combination of large-scale production facilities and genetically enhanced microalgae might be required to make algal biodiesel costs comparable to crude oil. Another consideration is the cost of oil extraction. Researchers at the University of Minnesota are studying oil extraction techniques to figure out what method is most efficient. In reality, cost-effective biodiesel may not be realized for many years, but as long as scientists and prospecting companies keep improving the process, chances are good that algal biodiesel will become a very viable future fuel.
Biogas
Biogas is one example of fuel that is currently used all over the world and needs no genetic manipulation of bacteria to make it cost effective. When soil bacteria digest organic material with no oxygen present, they produce methane and other gasses as waste products. Methane makes a great fuel and is the main component in both natural gas and biogas. This process occurs naturally in landfills, and many landfill sites capture the gas and purify it. This purified gas has a variety of uses from generating electricity to powering cars. There are already over 400 landfills in the United States that use this technology, but many more that could benefit from it. According to the Environmental Protection Agency (EPA), methane has a greater global warming effect than carbon dioxide; therefore, it is very important that all landfills collect biogas to prevent it from escaping into the atmosphere. The EPA currently has many assistance programs to help landfill operators set up gas collection systems.
Biogas is also a product of animal and agricultural waste decomposition by bacteria. Many farmers and dairy owners use biogas recovery systems to convert manure into fuel. This technique is especially popular in China and India. In fact, many families own small-scale digesters, which generate heating and cooking fuel for their own individual household. This practice is gaining popularity through rural parts of the world because of the availability of raw materials.
A variety of organisms is required for the production of biogas. They work synergistically. A microbe will digest what it can, and produce byproducts to be digested by others. This complexity means scientists have had difficulty figuring out the dynamics of these microbial communities. Genetically altering these bacteria to increase biogas production may not be feasible or even necessary. The future of biogas as a sustainable fuel instead relies upon increasing the rate of collection or improving methane purification.
Microbial Fuel Cells
Similar to the production of biogas, electricity from microbial fuel cells results from the bacterial digestion of organic matter. Microbial fuel cells work by converting a microorganism’s metabolic energy into a stream of electrons. When bacteria decompose organic matter, they produce electrons inside the bacterial cell. Some bacteria are able to expel these unwanted electrons to the outside of their cell wall. If an electrode is present when the electrons are expelled, these electrons will travel through it creating an electric current. As long as the microbes are fed, this process will continue to generate electricity.
The advantage of using microbial fuel cells is their efficiency. When biogas is turned into electricity, a lot of energy is lost in the conversion, but when electricity is produced from microbial fuel cells it happens in a closed system resulting in very little energy loss. Another exciting aspect of microbial fuel cells is their ability to treat and subsist on wastewater. Wastewater treatment plants presently consume a lot of electricity. Microbial fuel cell technology might help supply wastewater treatment plants with their own energy in the future.
Microbial fuel cells are still in the research and development phase. Scientists are figuring out what combination of organisms, fuel cell material, and size will result in the most electricity. Recent research at the University of Southern California has found that microbial fuel cells containing a combination of photosynthetic organisms and other bacteria will produce electricity with sunlight as the only input of energy. This process is more efficient than solar panels and uses mainly organic materials.
Bioremediation
Microbes can offer more than just fuel production. They have to ability to decompose a variety of materials, including toxic substances. This process can help restore contaminated environments to their natural condition. Traditional cleanup of chemical spills or other polluting events consists of digging up the contaminated area and moving it into a landfill or other location and dispersing it. This method takes a lot of effort, and yet does not directly degrade the offending contaminants. When a toxic substance eventually does get broken down, the process is often the result of bacterial activity from microbes found naturally in the environment. Scientists have discovered ways to exploit this bacterial activity by either increasing the population of bioremedial bacteria, or by increasing the rate at which these biochemical reactions occur.
Bioremediation is a complicated science. Similar to microbes involved in biogas production, many different species of bacteria work synergistically to break down toxic substances. Some of these activities are still a mystery and continue to be researched. Nevertheless, scientists have made great advances in this field. One example is the bioremediation of methyl tert-butyl ether (MTBE). This chemical was used as an oxygenating compound in California’s gasoline until 2002. When the carcinogen was discovered in water sources, California and many other states banned its use as a gasoline additive. Originally thought unsusceptible to degradation, MTBE is now decomposable by a variety of bioremediation techniques. Researchers at the University of California, Davis have a patent pending for a type of bacteria that is able survive with MTBE as its only food source.
Food Production
Bioremediation may also help restore agricultural lands to their natural state, contributing to sustainable agriculture. Microbes have the ability to break down residual pesticides and restore nutrients to the soil. They may assist crops in other ways too. Already there are many mutually beneficial interactions between plants and bacteria. Most of these interactions occur at the root/soil interface. Bacteria are able to supply many plants with the nitrogen and other nutrients they need. In addition, many types of bacteria that live on the surface of plants can confer resistance to disease.
These natural interactions have led to the study of biopesticides. Biopesticides consist of bacteria or other naturally produced substances that do not harm the plant, but kill plant pests. They can be applied just like regular pesticides, but do not contain toxic chemicals. More study is needed to see if this might be a natural alternative to traditional pesticides. If research indicates they are as effective and cause no harm to the environment, they might fully replace the synthetic pesticides used today.
Biodegradable Plastic
Another necessary product that contains toxic chemicals and could potentially be reduced or eliminated is plastic. Synthetic plastic has become a fundamental material in the modern world. It serves a variety of uses, both noble and trivial. Unfortunately, no matter how useful a plastic product has been, at the end of its lifecycle it will most likely end up in a landfill. Because plastic is such a durable material, it can take years to decompose. When it does, its toxic compounds are released into the environment. Plastic can be recycled, but recycling it is costly, and plastic can only be recycled a few times before it is structurally useless. These drawbacks have increased the demand for an earth-friendly plastic.
A number of possible alternatives to petroleum-based plastics have been discovered, but the most promising is family of substances called polyhydroxyalkanoates (PHAs). These substances, which are produced from bacteria, have properties similar to plastic but can biodegrade in water, soil, or sewage. Bacteria form PHA granules inside their cell for food storage, but to us they are much more. Once the PHA has been extracted from the bacteria, it can be treated just like plastic and turned into a variety of products.
Over the years, scientists have been focusing on increasing the bacterial production of these PHAs to make bioplastic more economically feasible. The solution for one company is genetically enhanced E. coli bacteria. This type of bacteria does not produce PHAs naturally, but has many other characteristics that make it a favorable candidate for production such as rapid growth and resilience. To make these specialized PHA microfactories, scientists combined genes from a PHA producing bacteria with the E. coli genes to make a new type of bacteria containing a changed DNA sequence. These new genes cause the bacteria to produce PHAs inside its cells. One of the leading companies in this endeavor is Metabolix, Inc, which has developed a cost-effective way to produce PHA. This company is currently constructing a production plant in Clinton, Iowa, in which to manufacture its Mirel™ bioplastic. According to the company’s website, the plant will be in full production mode by the middle of this year (2009).
From fuel to plastic, the abilities of microorganisms are phenomenal. They have to potential to help us create future security for our planet and ourselves. More research is needed to fully develop microbial potential, but government microbial research projects and private industry initiatives are showing great promise. It is up to us to continue to support research in this field.