The Cliff Notes on Biomass Fuels and Greenhouse Gas Levels Clean Air Task Force 18 Tremont Street Suite 530 Boston, MA Prepared for 2016 Northeast Biomass Heating Expo Burlington, Vermont March 30, 2016

2 Biomass fuels can reduce or increase greenhouse gas levels in the near term – it depends on sources, uses and timeframe It Depends

Burning biomass emits more CO 2 at the stack per useful unit of energy than fossil fuels Stack emissions for wood 3

Burning whole trees that would otherwise be long-lived increases greenhouse gas levels for the near term even if they are from sustained yield forestry 4

Adapted from Ter-Mikaelian, M. T., S. J. Colombo, and J. Chen The burning question: Does forest bioenergy reduce carbon emissions? A review of common misconceptions about forest carbon accounting. Journal of Forestry, 113(1): Effect of harvest for bioenergy to replace coal Forest carbon without harvest Carbon stocks at time of harvest Fossil fuel emissions avoided 5 Burning whole trees that would otherwise be long-lived results in a time delay for reducing greenhouse gas levels Increase in greenhouse gas levels Effect of harvest for bioenergy to replace coal – benefits accrue after reaching carbon sequestration parity

6 To stay below 2 o C cumulative emissions must stay below 790 billion tonnes of carbon This target is projected to be exceeded in within 3 decades Timing Matters 2oC2oC

Near term greenhouse gas levels matter – the median timing to maximum warming from emitting a pulse of CO 2 to the atmosphere is 10 years and most warming persists even after a century Temperature increase from an individual emission of carbon dioxide (CO2). Time series of the marginal warming in mK (=milliKelvin = K) per GtC (=1015 g carbon) as projected by 6000 convolution-function simulations for the first 100 years after the emission. Maximum warming occurs a median of 10.1 years after the CO2 emission event and has a median value of 2.2 mK GtC−1. The colors represent the relative density of simulations in a given region of the plot. (Ricke & Caldeira 2014). 7

Full regrowth is not guaranteed – with climate change and land conversion, forests may not sequester as much carbon in the future Projections of forest C annual change in the forest C stock (Tg yr−1), (C sequestered by forests (Tg yr−1), uses (Tg yr−1) for each of three land use scenarios: Constant forest area, Extrapolated forest area (based on previous 5 years change), and the Reference Scenario (transitions from extrapolated to constant at year 2032). (Wear and Coulsten 2015) 8 Depending on projected forest conditions to reduce GHG levels has inherent associated uncertainties

Sources that can reduce greenhouse gas levels in the near term, as well as the long, are: Logging slash Manufacturing wood waste Urban wood waste Trees that would die and decompose anyway (the supply of these is surprisingly large) As their carbon would end up in the atmosphere anyway in the near term (decades) 9 “Overstocked” Stands Slash Sawdust

Source: Jake Maier and the Cole Bros. Before thinning After thinning to reduce mortality and increase growth on crop trees A real opportunity to reduce GHG levels More wood dies in the Maine forest each year than is harvested (28 vs 17 million green tons [Ken Laustsen, MFS]). These emissions are equivalent to more than those from 5 million cars.

Acres of small diameter stands in Maine Source: Ken Laustsen, Maine Forest Service

These fuels could be increased significantly with the right policies, e.g., Build it With Wood (increases slash and manufacturing waste and may create markets for small/low quality trees) Expanding payments for early commercial thinning 12 Conceptual Design by Michael Green Photo from Mahlum Architects, courtesy W.G. Clark Construction

Biomass fuels can reduce or increase greenhouse gas levels in the near term 13

A productive path forward is to develop broad agreement on a policy that will use biomass fuels productively to reduce greenhouse gas levels in the near as well as long term. 14 Biomass heating does offer real opportunities to reduce GHG levels

Most beneficial use of wood for reducing GHG levels is long-lived wood products with residues used as fuel 15 Simplified, but based on Figure 5.12 and Table 5.2 from Matthews, et al. (2014). Oliver, et al. (2015) estimates that global CO 2 emissions could be reduced by 14-31% by substituting wood in construction and for fossil fuel