Biogeochemistry: the recycling of elements in nature

Solid waste from livestock manure, waste-water treatment plants, and landfills can be anaerobically digested to produce biogas methane for multiple uses, with many ancillary benefits. | Illustration courtesy of Colorado State University Extension and University of Maryland Center for Environmental Science

Most global citizens could probably do a better job of conserving energy and recycling the materials used every day. Why not take a few pointers or get inspiration from nature— it has been perfecting its strategy of sustainability for eons.

Scientists and engineers have already created man-made systems capable of almost every service provided by plants and animals, but it is doubtful those systems would be considered as beautiful as a willow oak, nor as tasty as a blue crab, nor provide all the ancillary services and benefits of those self-replicating living systems. They also cost a lot more and require a great deal of maintenance, materials, labor and energy inputs.

For example, if you are undersea in a modern submarine for a few months you can make your own fresh water, off load carbon dioxide, and even make your own oxygen to breathe, but it requires the energy of an on-board nuclear power plant and a highly specialized crew that is just a tiny fraction of our population.

Microbes at landfills break down carbonaceous waste into the flammable gas methane. That methane can be purified, and even compressed for transport, to provide flame for heat, direct combustion or steam production for generating electricity, or even directly powering vehicles. There now exists landfills where trucks at the landfill run on methane generated by the landfill. | Microbes at landfills break down carbonaceous waste into the flammable gas methane. That methane can be purified, and even compressed for transport, to provide flame for heat, direct combustion or steam production for generating electricity, or even directly powering vehicles. There now exists landfills where trucks at the landfill run on methane generated by the landfill.
Microbes at landfills break down carbonaceous waste into the flammable gas methane. That methane can be purified, and even compressed for transport, to provide flame for heat, direct combustion or steam production for generating electricity, or even directly powering vehicles. There now exists landfills where trucks at the landfill run on methane generated by the landfill. | Stock illustration via Pixabay

Eventually, when the MRE’s ran out, you would also need to get wet to get a lobster, and swim ashore for a steak, for a “surf and turf” dinner to keep crew morale high. If the man-made capsule you are living in is orbiting earth, your menu choices would be even fewer.

Oxygen, water, food, raw materials, and transportable energy are the basic material needs we must manage for our survival and prosperity. How, and in what form, we obtain those items can sometimes be challenging for more than seven billion people on a single planet, or even a small isolated force in a hostile environment.

Meeting those needs for ourselves and others long into the future takes planning and good strategy. Fortunately nature is full of organisms and sun-fueled systems that can serve those needs very efficiently, cost-effectively, and sustainably for us long into the future— if we give them the space and conservation they need. You might say it is natural resource stewardship at the molecular level.

Biology, geology, and chemistry, oh my

Most young students learn about the cycling of water, minerals, and other elements in a basic science class in school.

Besides water, some of the other important cycles are those for carbon, nitrogen, phosphorus and sulfur, all of which are key elements necessary for life. There are solid, liquid, and gaseous forms of most of these that cycle between the soil, water, air and living organisms.

Everyone generally has an even better understanding, and personal experience, by observing how living organisms’ cycle between life and death, and how species are sustained over time through offspring.

In biogeochemistry we try to better understand, at the molecular level, and microbial level, how all of these living and non-living components, materials and energy, are interconnected.

We can easily observe the vulture and crab recycling the dead organisms of land and sea. We may even be so unlucky to witness termites recycling the wood in our houses. As rural homeowners, we may experience the importance of keeping toxins like bleach out of our septic tanks, to keep the microbes inside alive so they can process our waste agreeably, before it ultimately drains to our aquifers or Bay.

At the smallest level, the real living drivers of many of these cycling processes are microbes. In fact, even in the case of a termite, it is actually the microorganisms in his gut that produce the enzymes necessary to break down the cellulose in the wood and thus return elements to the soil and air for the next tree or flower.

Human activity and ingenuity have altered the cycles of many of earth’s minerals, other elements, and molecules to our advantage. However, the most sustainable versions of those systems, are the ones that don’t significantly change the overall balance of these molecular and microbial cycles, and may even mock natural cycles to become more efficient and sustainable.

Using microbes to recycle waste and create fuel

An increasing number of landfills, wastewater treatment plants, and dairy farms have started employing microbes to recycle and reduce their large volumes of solid waste, while at the same time creating a useful product called “biogas”.

These unique and useful microorganisms share some characteristics with bacteria, but in fact are an entirely different domain of living things called “Archaea”. Many from this domain live in extreme environments of high heat, high salinity, or no oxygen.

Many of the ones that live without oxygen are known as “methanogens” for their ability to break down carbonaceous waste into the flammable gas methane. Buried sediments, buried trash, or human or animal waste can have little or no oxygen and lots of carbonaceous “food” for these microbes.

Like us, their gaseous waste can also contain carbon dioxide, and so that is sometimes removed to make a more pure form of the methane fuel, known as “renewable natural gas” (RNG). The methane fuel can be purified, and even compressed (CNG) for transport, to provide flame for heat, direct combustion or steam production for generating electricity, or even directly powering vehicles.

There now exists landfills where trucks at the landfill run on methane generated by the landfill. Not exactly a natural cycle but a very efficient one that also helps our atmosphere by converting the methane molecules into the less destructive (less warming potential) carbon dioxide molecules.

Biofuels from waste are being explored by the Army for vehicles, by the Navy for ships, and by the Air Force for fighter jets. Once produced, the fuels are basically the same types of hydrocarbon molecules as ones already used, but the cost and technology of their production and distribution is still being developed to be competitive with conventional petroleum-derived non-renewable fuels.

Economic comparisons are also difficult because biofuel has other benefits whose monetary value is difficult to quantify. Those benefits include: less dependence on non-renewable fossil fuels; solid waste disposal and volume reduction; production almost anywhere humans or animals are generating solid waste; potential for development to be self-funding; and production on-site with no need to transport for use for heating, cooking, or generating electricity.

Imagine a large ship or base being able to reduce the volume of human, food, and paper wastes, on-board or on-site, by anaerobically digesting it into methane fuel for a variety of applications.

Human and animal waste to energy

In the case of the waste-water treatment plants and dairy farms, not only is biogas fuel produced, but the remaining solids are also a more stable and hygienic fertilizer product than the raw solid waste. Modern environmental engineers apply biogeochemical science to design more environmentally and economically sustainable systems for meeting human needs and recycling our wastes.

Sometimes, only minor engineering is needed to use recycling “machines” already found in nature like trees or wetlands to inexpensively reduce the total maximum daily loads, total suspended solids, nitrogen, and phosphorus wastes from entering surface waters like the Chesapeake Bay. With a little more human engineering, rain barrels and rain gardens can also help.

The plants in these more natural systems can also sequester carbon from our atmosphere and provide other services in the process. In the case of large herd dairy farms, or large city waste-water treatment plants, more expensive human-engineered systems are necessary to convert the tremendous volumes of waste to energy safely on a small piece of real estate.

New York City and Baltimore have both built systems to anaerobically digest municipal human waste to produce biogas fuel to power systems and offset waste disposal costs. The main sanitary landfill in Wicomico County, Maryland captures and sells the methane generated from their buried garbage to a private company that burns it to generate electricity. Pilot tests of anaerobic wastewater treatment plants that produce methane fuel are being performed at Fort Riley, Kansas, and at Mountain Home Air Force Base, Idaho.

A more sustainable future in the hands of young engineers

In spite of currently (and relatively) low oil prices, there is increasing interest worldwide in developing better waste to energy systems on both the large scale and for smaller applications.

A new generation of scientists and engineers in universities, government agencies, NGO’s, and private companies (including the large conventional oil companies) worldwide are exploring new and efficient ways to apply biogeochemical cycles to the production of renewable energy while solving other environmental and economic challenges. It is necessarily an interdisciplinary science with many challenges and many opportunities for budding engineers and scientists.

This summer, the Army Educational Outreach Program (AEOP) at APG will include a GEMS3 (Gains in Education of Mathematics and Science) course for high school students on Alternative and Renewable Energy. Two days of that course will be spent exposing students to waste to energy technology with lab activities, guest scientist speakers, and projects.

APG natural resources managers have a long history of continually coordinating the natural infrastructure stewardship that supports and sustains the Army’s testing and training mission every day. Working with partners from APG tenant organizations, the U.S. Fish and Wildlife Service and the Maryland Department of Natural Resources, APG DPW personnel developed and coordinated our Integrated Natural Resources Management Plan (INRMP) as a roadmap to the future for APG natural resources management.

By John Leader, APG Directorate of Public Works, Natural Resources Team

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