Environmental Engineering Reference
In-Depth Information
An even less expensive potential solution is The Peepoo
s
, a single use, self-sanitizing, bio-
degradable bag that can be used to capture human waste, which can be used as fertilizer
just two to four weeks later (
http://www.peepoople.com/
)
.
Some methods are being used to recover P that is normally considered too diffuse or
too difficult to recapture. Algal turf scrubbers (ATS) are an engineered system for flowing
water over surfaces with naturally seeded filamentous algae that can later be recovered
and used as a nutrient source on farms (
Adey et al. 2011
). The fast growth of algae on ATS
means that this technology has the potential to remove nutrients at high rates. A pilot
study in the Florida Everglades recovered up to 0.14 g P m
2
2
day
2
1
, roughly two orders
of magnitude greater than the P capture of managed wetlands in the same region. Other
studies of using ATS flowways with dairy manure effluents indicate that these systems
can capture 40% to 100% of input P, depending on the P loading rate (
Mulbry et al. 2008
).
Finally, consideration of how demand for P will change in the future is essential. Global
demand for P is forecast to increase by about 3% to 4% annually, primarily in Asia (
FAO
2007
). This demand is affected by human diets, by trade, by methods of agricultural
production, and by access to fertilizers. For example, increases in demand may come from
growing crops for bioenergy. Approximately 10% of fertilizer use in the United States is
applied to corn that will be used to produce ethanol (
Childers et al. 2011
). Other increases
in P demand may come from increasing population, increased urbanization, or changing
diets. In 2003, an estimated 2 billion people ate a meat-based diet, while an estimated 4
billion lived primarily on a plant-based diet (
Pimentel and Pimentel 2003
). Diets in rapidly
developing countries such as China are now increasingly shifting toward a diet heavier in
meat as people grow wealthier (World Resources Institute 2012).
SUMMARY
Phosphorus is a critical element, playing an important role in limiting or colimiting
primary production in many terrestrial and aquatic ecosystems. This importance has
stimulated a great deal of recent research into P cycling in many ecosystems and the
human impact on P cycling. As we face increased demand for P to fertilize agricultural
crops and globally limited P supply, understanding how P moves within and across
systems will become ever more important. Our current understanding involves factors
that affect P movement at local, watershed, and global scales. The next steps will certainly
be in the area of understanding interactions across scales.
References
Abbas, F., Merlet, J., Morellet, N., Verheyden, H., Hewison, A.J.M., Cargnelutti, B., et al., 2012. Roe deer may
markedly alter forest nitrogen and phosphorus budgets across Europe. Oikos 121, 1271
1278.
Adey, W.H., Kangas, P.C., Mulbry, W., 2011. Algal turf scrubbing: Cleaning surface waters with solar energy
while producing a biofuel. BioScience 61, 434
441.
Bennett, E.M., Carpenter, S.R., Caraco, N., 2001. Human impact on erodable phosphorus and eutrophication: A
global perspective. BioScience 51, 227
234.
Carey, C.C., Ewing, H.A., Cottingham, K.L., Weathers, K.C., Thomas, R.Q., Haney, J.F., 2012. Occurrence and
toxicity of the cyanobacterium Gloeotrichia echinulata in low-nutrient lakes in the northeastern United States.
Aquat. Ecol. (in press).
