By Sally Brown, University of Washington
Abstracts of these resources are available in the searchable Information Portal offered to Northwest Biosolids members.
Long-term amendment of urban and animal wastes equivalent to more than 100 years of application had minimal effect on plant uptake of potentially toxic elements
How does recycling of livestock manure in agroecosystems affect crop productivity, reactive nitrogen losses, and soil carbon balance?
Accelerating innovation that enhances resource recovery in the wastewater sector: advancing a National testbed network
Contributions of local farming to urban sustainability in the Northeast United States
Adapting cities for climate change: The role of the green infrastructure
I have fond memories of SNL even before Alec Baldwin became a regular on the show. In particular I remember Rosanne Rosannadanna (aka 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. That 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 US 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 this 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 it is possible to 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 N 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. 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 here? The third article is a start of the answer to that. Here a big group of scientists got together to write about the best way that we can decide how to treat wastewater with the least expenditure of energy and 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 4th 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) 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 US, 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 stormwater flows. So perhaps research and outreach for use of biosolids in urban areas has benefits above and beyond reduced transport 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, it is time to shift the focus to optimizing benefits.