Tag Archives: agriculture

Waste Resourcing

What exactly do we consider “waste”? Could what we are flushing down the toilet be more important than we realize? We are constantly in search of supplies to burn for energy and grow to eat, but what leaves our body we tend to want to overlook. New technology is developing that may be able to take advantage of that we currently label as waste, which holds both nutrients and biomass. Recycling of these resources can help mediate the depletion of natural supplies from our energy and agriculture demands.

image by Olearys via Flickr

Nutrients which are necessary for plant growth–such as nitrogen phosphorous and potassium– are all excreted after we consume those plant foods. Humans use raw deposits of these minerals for fertilizers, which have been estimated to contribute to 30-50% of crop yield. Before this discovery humans were using guano (sea bird and bat excrement) in crops to promote growth. These nutrients are essential for our ever growing agricultural industries. Meanwhile, their natural deposits are quickly declining due to our own demand. The following video discusses the problem of diminishing phosphorous:

Similar problems are faced for other nutrients such as potassium; while having a longer projected depletion time of 330 years this estimate does not account for accelerated use for grain crops or depleted soils. Potassium as well as nitrogen prices are estimated to steadily incline over the next 10 years.

Another depletion that can be mediated though waste sourcing is fossil fuels, which we use as an energy source. Organic material (also known as biomass) in sewage can be converted into methane gas and used as a fuel source which can serve as a green source of energy for our growing demand. As fossil fuels also have a diminishing raw supply it is imperative that reliable alternate energy sources are found. Potentially using waste biomass as a carbon source would provide a sustainable and economical source of energy. Although sewage biomass will not be able to replace fossil fuels, it is still a completely green fuel source that can make a contribution to our demands.

Are these recoveries realistic? There are two leading processes for waste treatment: Lower Energy Mainline (LEM) and Partition-release-recover (PRR).

image by Montgomery County Planning Commission via Flickr

Both processes target nutrient preservation while recovering energy. LEM is by far more cost efficient and results in net energy recovery and full phosphorous recovery, but very low nitrogen recovery. However, due to it’s cost efficiency it is likely to be used in the near future. PRR on the other hand results in large enough concentrations of nitrogen and phosphorous for extraction of both, but it more energy intensive.

As our technology advances the field of waste treatment will become more and more efficient. Resource availability is a serious threat, but being able to take advantage of our waste can create a much more sustainable society. Slowly implementing these advancements can bring us closer to a circular economy; one that does not depend on sources being depleted from natural deposits.