I have fond memories of Saturday Night Live, even before Alec Baldwin became a
regular on the show. In particular, I remember Rosanne Rosannadanna (a/k/a Gilda
Radner) and her opinion segments on the Weekend Update portion of the show. She
would rant on and on and then Chevy Chase would point out that there was really
nothing behind her argument. She would quietly say ‘Never mind’ and the show
would move on.
Rosanne Rosannadanna is basically the jist of the first paper in this month’s library.
Scientists from Scandinavia, of all places, look at metal availability in biosolids and
say, ‘Never mind’. In general, European soil scientists have had much greater
concerns about metals in biosolids than U.S. scientists. The paper reports on results
from a field trial where a range of soil amendments. including biosolids and
composts from MSW. were used. While the authors note that the old kind of ‘sewage
sludge’ was high in metals and posed a risk, this new stuff is clean and is just fine to
use. In fact, they note that the higher plant Zn in the biosolids treatments is a good
thing, as zinc is an important micronutrient. If scientists in Scandinavia can move
on, perhaps it is time that we all moved on.
If you can get past the contaminant de jour, then possibly you can recognize that
biosolids share many characteristics with animal manures. Sure, biosolids are more
tightly regulated and have more consistent pathogen kill, but both are primarily by-
products of animal digestive systems. With anaerobic digestion, the nitrogen in
biosolids is perhaps more slowly available than the nitrogen in animal manures -- so
much the better. The second study in the library is a meta-analysis (read, major
literature review) of the performance of animal manures compared to N fertilizer.
Surprise here! Manures work better than fertilizers; better crop yield, more soil
carbon sequestration, lower N loss and (except for rice paddies) lower fugitive gas
emissions. Take away that special paranoia typically reserved for biosolids and you
can recognize that the results here almost certainly apply to biosolids as well.
So, no need for concern and in fact many reasons to promote. Where do we go from
The third article is a start of the answer to that question. Here a big group of
scientists got together to write about the best way to decide how to treat
wastewater with the least expenditure of energy and the greatest capture of
resources. They talk about the high return on investment that research dollars
bring to environmental processes such as wastewater treatment. Even if that is
true, they also note that federal funds are not forthcoming. They propose regional
research centers or networks that would make such efforts more efficient and
potentially even feasible. Sound familiar? We already have similar networks in our
regional biosolids management associations. More and more, these networks are
recognizing the potential to use biosolids within the limits of the wastewater
districts themselves. Local uses are often preferred as they can reduce transport costs and make stakeholders more familiar with the wastewater process and products. But local uses have additional value. For that we go to the last two articles in the library.
The 4 th article talks about the impact of locally grown food in the Boston area. The
authors use a range of sophisticated models to evaluate the potential to grow food in
the city, the carbon impact of local food production, the economic impact and the
nutritional impact. The authors consider the whole diet and, with that perspective,
the impacts of urban agriculture are minimal. Meat and dairy are the most carbon
intensive things we eat and the most difficult to grow on a rooftop. When they limit
their analysis to garden produce, the results are much more encouraging. Urban
agriculture in the highly dense Boston area has the potential to use 10% of all
compost produced (here the focus is on solid waste not biosolids) and to generate
significant revenue and improve diets. They also discuss the potential for growing
foods on contaminated soils following remediation. In other words, for most of the
municipalities in the U.S., using biosolids soil products for urban agriculture can
have a big and very positive impact.
The final article looks at the potential for green infrastructure to help urban areas
deal with climate change. Here the focus is on Manchester, England. Going green
can reduce the heat island impact by several degrees and can also make a significant
impact on storm water flows. So perhaps research and outreach for use of biosolids
in urban areas has benefits beyond reduced transportation costs.
As we come to realize the importance of resource recovery and the many and varied
ways that use of biosolids can enhance our environment rather than destroy it,
additional opportunities and benefits will be recognized. While I can’t say it is OK to
ignore concerns about contaminants, the time has come to shift the focus to
Sally Brown, University of Washington