byon November 20, 2008
A mop-up crop, simply put, is a crop that pulls contaminants out of the soil. Well, hemp has been shown to pull heavy metals out of the soil, but apparently it can also help used in sewage treatment.
You see, raw sewage is a problem for water because it causes eutrophication, which is when so many nitrogen and phosphorus nutrients seep into the water that most life cannot survive. Basically, these nutrients cause so much algae to grow that fish life suffocates. Next thing you know, there’s nothing but algae living in your water — and that’s not much of a diverse ecosystem.
Eutropihication is most common when manure fertilizer and other farm animal waste runs off into the water table. But imagine if you were dumping that manure directly into streams or river. Well, that’s pretty much what we do with sewage.
Well Keith Bolton, Chief Scientist and Director of Ecoteam, recently conducted some trials using a variety of fiber crops to as a mop-up crop in sewage treatment, and hemp greatly out-performed all the other crops. Collaborating with a water treatment company, Bolton irrigated a hemp crop with sewage, and teh hemp absorbed 90% of the nitrogen. Also of interest was that at one point, someone dumped ammonium into the sewage, and the hemp absorbed 95% of that.