Saturday, May 3, 2014

Harvard University Site Converts to Renewable Thermal Biomass...while Gathering Data to Make or Break the Case for Biomass

MA state Biomass consultant Rob Rizzo chats with David Foster
Harvard University Site Converts to Renewable Thermal Biomass...while Gathering Data to Make or Break the Case for Biomass

By Genevieve Fraser

As the biomass controversy continues in some quarters, Harvard University has taken a bold move with a non-fossil fuel energy efficient solution to some of their heating needs with a biomass boiler to heat five of their buildings.  But unlike typical biomass solutions, this system is a gasification model that uses cordwood instead of wood chips.  In keeping with true energy efficiency, Harvard’s venture is installed at their Harvard Forest location, a 3200 acre land base in Petersham and Phillipston. Basically, the wood is harvested on their site and trucked a short distance to their pole barn.
Senator Steve Brewer addresses gathering at dedication of biomass facility
But Harvard – true to its educational mission – doesn’t stop there.  The  biomass gasification system is viewed in a larger context.  Harvard University conducts forest biology and conservation research on the property, including two major programs: the Long Term Ecological Research LTER program, funded by the National Science Foundation and established in 1988 to investigate New England's natural ecosystem; and the National Institute of Global Environmental Change program established and funded by the United States Department of Energy and emphasizing the study of physical and biological processes in relation to climate change. Harvard Forest is also slated to be the northeastern core site of the National Ecological Observatory Network. A number of smaller research programs are also conducted in Harvard Forest.
David Foster leads a walk into Harvard Forest

According to Harvard Forest’s director David Foster, “With this project, we are putting our assertions into practice and providing a practical application to our fundamental research exploring the role of forests as infrastructure.  We can address looming questions about carbon dynamics, and the linkages between conservation, use of resources, and the way our land can figure in as a solution toward climate change.”
“The Harvard Forest in Petersham has long maximized using renewable sources for energy and heat. The trees used to fuel the boilers are harvested as part of a sustainable management plan. The woods crew focuses on taking low-quality material out of the forests for use as biomass, therefore improving the growth and quality of trees with a higher economic and ecological value.”

“One of the very clear facts is that if you look across New England and most landscapes, it is direct impacts by people that are having the strongest effect on changing natural process,” Foster said.  “Our recent ‘Changes to the Land’ report showed that the greenest scenario for the long-term viability of nature and society is not only to conserve but actively to manage the land.”

In terms of the data gathered at the site, the Harvard Forest website offers the following:

Forest Management and Carbon Dioxide
A selective, commercial harvest adjacent to Harvard Forest provides a unique opportunity to monitor changes in the distribution and amount of Carbon sequestration in a managed forest. The suite of ecological measurements used in the tower footprint was duplicated in 6 additional plots randomly spaced through the harvested site.  Additional measurements on these plots include soil moisture (TDR method) and extended soil respiration. Following the harvest, measurements in the plots will continue, documenting changes in rates of respiration, tree growth, and other biological processes affecting carbon balance.  To complete the picture of the effects of harvest on carbon balance, the fate of saleable wood C will be tracked and compared to other harvests in the Northeastern region.
Carbon Exchange.

Harvard Forest tower-based CO2 measurements examine how regional and ecosystem level processes in a mid-latitude forest contribute to global carbon cycling.  Specifically, we endeavor to understand quantitatively how and why forested ecosystems take up or release carbon, on time scales from hours to decades, and to elucidate responses to climate changes and management interventions. 
The tower was installed 1989 and the resulting eddy-flux measurements constitute the longest running record of the net-ecosystem carbon exchange in a North American Forest.  The resulting long-term record of Net Ecosystem Exchange (NEE) has shown the effects of climate anomalies on carbon fluxes for seasonal and annual time scales. For example, reduced soil frost allows greater respiration in the winter leading to lower C sequestration. Cumulative gross photosynthesis depends on when the canopy emerges in the spring.  Warmer springtime temperatures lead to greater uptake of C.  These earlier results are reported in the 1996 Science paper, "Exchange of Carbon Dioxide by a Deciduous Forest: Response to Interannual Climate Variability" (abstract).  The longer term trend of net uptake (2 tC/ha/yr on average) however is likely driven by succession of red oak to dominance over earlier pioneer species, enhanced by recent trends towards warmer spring temperatures and associated earlier canopy development.  In short, the major factors that regulate carbon sequestration appear to be recovery from prior land use, length of the growing season, snow cover, cloudiness, and drought. 
In 1993, ground-based ecological measurements were undertaken to compliment the tower-based measurements of CO2 exchange.  High resolution dendrometer measurements, soil respiration chambers, vegetation surveys, leaf area index (LAI) measurements, leaf nitrogen analysis, and litter collection have all been implemented in 40 plots in the tower ‘footprint’ which spreads from the northwest to the southwest of the tower.  Defining individual rates for these major biological processes will allow assessment of individual contributions from gross photosynthesis, C storage (by wood increment), and autotrophic and heterotrophic respiration to the net carbon flux.
Senate Committee on Global Warming and Climate Change chair, Senator Marc Pacheco
discusses biomass potential with David Foster

As the NEE record is extended and augmented by supporting ecological measurements, we can further identify longer-term effects of climate perturbations on carbon fluxes and further define the relationship between stand history and carbon sequestration.  Climatic anomalies in one season or year may have a longer term effect on the sequestration of carbon in subsequent seasons or years.

The flux and ecological measurements are coordinated with studies at other sites through the AmeriFlux network. By examining the relationships between carbon fluxes and the driving physical and biological variables across a range of sites we are enhancing understanding of the processes that control NEE.  Data from both the tower-based and the ecological measurements are available through our data exchange.
Dioramas at Harvard Forest's Fisher Museum

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