Sunday, June 03, 2007

Sewage to fertilizer

A large sewage treatment plant in Oregon is testing a process to make fertilizer from sewage. The process, from a Canadian company, is advertised as a win-win process that saves money and turns waste into a useful product.

The process uses Magnesium to capture phosphorus and ammonia and turn it into BB-sized pellets that can be spread as fertilizer. So long as there are no problems with toxics in the sewage, it ought to work.

Now about their proposal to put some of the fertilizer in streams to fertilize salmon production. Nice try, mimicking the natural nutrient delivery of dead salmon carcases, but I've seen this idea misused in the past. Most of our streams need fewer nutrients, not more. And pellets are not the same as salmon carcases, which are eaten directly instead of just fertilizing plant growth.


Anonymous said...

Sounds very risky due to contaminants. Are there still levels of many contaminants that can be introduced? We have enough contaminans in all of our streams already. There are many streams that are lower in certain micronutrients, that used to be supplied by returning salmon and lamprey, and without this marine-derived- nutrient (MDN)young salmon may not have some essential micronutrients. The result might be reduced fitness, and could contribute to near-ocean-entry population decline. We cannot simply replace the complexity of MDN by only redesignating various toxic wastes as 'nutrient additives' if harmful contaminants still remain in the product. Buyer beware. Maybe they have all the bases covered, but somehow I doubt it.
Ray Kinney

Fromartz said...

I wouldn't use this stuff in my garden, let alone allow it in streams, because of the prevalence of heavy metals in sewage sludge.

Mark Powell said...

Agreed, sewage to fertliizer is an attractive concept but risky. I too doubt that the contaminants will be removed, and I think that salmon fertilization is a well-intentioned mistake. As a fishery biologist friend said about some restoration projects: the road to hell is paved with good intentions. We know about many "restoration" projects from 20 years ago that have been cleaned up at great expense in recent years. Oops.

Hodad said...

malofganite from human composted waste is some of the best fertilzer there is, however it is much better if the humans are vegetarians, lol
as far as heavy metals, that argumant does not hold and then again in a healthy human, we have the ability besides healing ourselves to rid the body of heavy metals but these would not transfer per se in fertilization of plants
any use of sewage and garbage in a 'sustainable means' is a good thing
India has large scale bio-gas composters
just a little maintenance is required,
but to use in this 'residue' in any animal fertilization is ludicrous
plants yes, animals no way