- Does the Billion-Ton Update include estimates for algal biomass?
- What is the significance of a billion tons? Is it a goal?
- Does the update reduce the land for food and feed? Will the U.S. still produce corn for export?
- Do biomass projections account for weather events related to climate change? (TAC)
- Why were some biomass feedstocks excluded?
- Why is irrigation excluded?
- If you remove stover and forest residues, won't you harm the soil?
- Why do some states not have woody biomass from forest thinnings?
- Were impacts to wildlife from land-use change estimated for the production scenarios?
- The biomass prices cited only include farmgate production, and don't cover transport and storage losses and costs. Is there any way to get even an estimate of what these costs would be?
- How do these feedstock production estimates compare to the DOE Multi-year Program Plan (MYPP) estimates (U.S. Department of Energy, 2011)?
- What is leading to the doubling of primary agricultural residues supply assumed in the high-yield scenario over the baseline?
- What are the implications of the study assumptions?
- The supply projections assume that land is shifting from potential food production to biomass production. "Under baseline assumptions, up to 22 million acres of cropland and 41 million acres of pastureland shift into energy crops by 2030 at a simulated farmgate price of $60 per dry ton."
- Could forest biomass from fuel treatments, or thinning, which is practiced in many areas for forest fire mitigation, be a sustainable source of biomass?
NOTE: These responses are provided by the study authors to address frequently asked technical questions about the study.
1. Does the Billion-Ton Update include estimates for algal biomass?
Algal biomass was not included in the 2011 U.S. Billion-Ton Update because there was insufficient data to estimate and project the availability of algal feedstocks at a county scale with any degree of accuracy. The Department of Energy (DOE) Biomass Program is funding an initial strategic national assessment of the resource potential of algae grown for biofuels, but more work is needed before there are enough credible public data to consider algal biomass to the same level of detail as terrestrial-based feedstocks in the U.S. Billion-Ton Update.
Very little algae are being produced today commercially. As a result, actual field data on the productivity for a variety of algae strains are not available. These data will be complex as productivity will need to be evaluated under different daily and seasonal temperatures, solar resource regimes, as well as weather-related events. In addition, the aquatic algal cultivation and processing systems are still being designed, which may further add or subtract from current productivity estimates.
A recent study conducted by the Pacific Northwest National Laboratory, sponsored by the DOE Biomass Program, indicates a U.S. potential of several billion gallons of additional renewable fuels from algae that can be produced on lands with poor soil quality using non-fresh water., This resource assessment effort will serve as a foundation on which to conduct more thorough national assessments as more data become available. The DOE Biomass Program is excited by the potential of algal feedstocks to add to the total U.S. biomass supply identified in the U.S. Billion-Ton Update and will continue to integrate algae into the research pathways and analyses as more public data are generated, reviewed, and accepted.
Continue discussing this topic in the KDF forums.
The 2005 study reported the potential to produce a billion dry tons annually, which, at that time, was roughly equivalent to displacing 30% of U.S. oil consumption (by volume) with biofuels by 2030. The 30% goal was one envisioned by the Biomass Research and Development Technical Advisory Committee in an earlier report as an amount large enough to attract major private-sector investment in biomass and significantly reduce U.S. reliance on imported oil. There is no specific goal related to usable energy in this report.
The study looks at the potential to develop various biomass resources without regard to their final use or user. Two charts show total potential biofuels and biopower amounts under specific assumptions (Figures 6.1 and 6.2). Specific assumptions are applied to estimate these volumes and capacity, namely a 20% handling and storage loss, 85 gallons per dry ton, and 13,600 BTU per kWh across all potential sources. In reality, these technical parameters may vary across time, region, choice of conversion, and feedstock. However, this direction of analysis was beyond the scope of this report.
DOE's research and development initiatives on biofuels aim to advance technologies and sustainable biomass resources that can provide energy without impacting food production. The POLYSYS model, an agricultural policy modeling framework, was used to estimate potential land-use change and potential economic impacts. The model ensures that all demands for food, animal feed and forage, and exports are met based on USDA's projections and our extrapolation. This includes the future growth in agricultural commodity exports. Commodity demand can be met not only by planting additional acreage but also by increasing yields and promoting more intensive management of hay and pastureland for livestock.
Yield estimates used in the report for major crops align with the USDA Agricultural Projections up to 2018, which assumes “there are no shocks due to abnormal weather, further outbreaks of plant or animal diseases, or other factors affecting global supply and demand” (p. i). For forest resources, dead and dying trees from incidents included in the 2009 FIA forest estimates (from Thompson, 2009) are actually included in the potential supply of forest residues. This “annualized” mortality was determined to be a better estimate than additional analysis for areas that had been subject to particular events. For more information, see Text Box 3.7 (p. 34) in the report.
The report focused on estimating supply curves for primary biomass feedstocks, i.e., biomass collected or harvested from the land. These are the feedstocks identified to have a large potential at this time. The study also included supply estimates for some secondary and waste resources. The authors recognize there are other potential feedstocks especially those that are only available in certain regions and states. Including an exhaustive inventory of all such potential feedstocks was well beyond the scope of the study, especially when their aggregate total is relatively small compared with the primary feedstocks identified in this report.
TIrrigation of energy crops can be a contentious issue. Water in the western United States has to meet a number of competing off-stream uses, such as municipal, agriculture, and industrial uses, as well as providing for hydropower generation and minimum in-stream flows for recreation and fisheries. In the West, the majority of water comes as winter precipitation, as rain or snow, and most water available for summer use comes from snow melt or storage.
In the western United States, most crops, including hay crops, are grown under irrigation. Irrigated energy crops probably may not compete economically with high-value irrigated crops, but under some specific conditions energy crops may be grown competitively under irrigation. One potential energy crop species that could be suitable for irrigation in the western United States is switchgrass, which has high water-use efficiency. Some grasses may be able to produce biomass under limited irrigation, under conditions and on lands where other traditional crops might not produce a product (e.g. feed suitable for livestock feed). The response grasses have to limited irrigation is species specific. Of course, producers' decisions about land and water use will continue to be market and value based.
Energy crops may utilize water that cannot be used for crops or human consumption, such as water from treated sewage waste, food processing, and mining and other industries. Significant quantities of produced water are extracted with oil, gas, and coal-bed methane, which could also be used to grow dedicated crops for energy production. Energy crops may also utilize marginal lands, where farming for food is difficult, including saline-affected land. This 2011 analysis did not examine the biomass resource potential that could be gained by using gray and recovered water.
For energy crop production to be profitable and competitive under irrigation, it will need to generate high yields to offset irrigation costs.
The analysis in the 2005 Billion Ton Study was based on the assumption that sufficient agricultural and forestry residues would be left on-site to protect the soil from erosion and maintain soil productivity, or that producers would replace lost nutrients with fertilizer. The updated study addresses more recent concerns over maintaining soil carbon. For corn stover, a new retention tool was developed to use site and weather parameters to estimate the retention levels that should protect soil from erosion and ensure long-term productivity and soil carbon. For forestry, an extensive literature survey was conducted to determine acceptable retention rates and these were applied for the slope classes.
For woody feedstocks from forest thinnings, the study assumes that to be cost effective, forest thinnings had to be removed along with merchantable products, such as lumber. A state-by-state analysis was completed to determine how much extra biomass could be harvested based on the current processing capacity for merchantable products from forests in each state. This information has been posted on the KDF as supplemental documents. In many of the states, the biomass potential was reduced by as much as 96% because of this assumption. As an example, Colorado has severe insect populations that would benefit from thinnings, but only a marginal amount, about 20%, of the biomass was counted because of the lack of facilities to process the merchantable portions.
Field-tested best practices for wildlife management were applied in the energy crop production scenarios. Some of the experts who worked on the analysis had wildlife management experience or had collaborated with wildlife specialists on projects relevant to their contributions to the report. The authors anticipate that there will be some specific onsite habitat changes, including some improvements such as the replacement of row crops with grasses, across the agricultural landscape. However, the authors expect the distribution of energy crops, row and forage crops, pastureland, and even woodlands to be a diverse mosaic that retains natural aquatic and terrestrial ecosystems that exist today. The models used for the report were not able to explicitly simulate changes to wildlife habitat, but an examination of the amounts and distributions of the energy crops in the counties on the KDF should generally provide the research community the opportunity to validate this concept. Data and models are needed moving forward to estimate and mitigate any wildlife impacts.
The total costs of feedstocks up to the biorefinery would require adding the transport, handling, storage, and preprocessing costs to the estimates in the report. The percentage of these costs compared to total feedstock cost would vary significantly by feedstock, conversion system requirements, and technology developments over the next 18 years. The additional cost beyond the farmgate or roadside is estimated to be about $16-27/dry ton in 2012, depending on the feedstock and conversion technology (DOE Biomass Multi-Year Program Plan, April 2011, pp.2-22-2-23).
The authors make an effort to point out to the reader that the prices and costs in the report do not include storage and delivery to the biorefinery. For example, beyond the Executive Summary and reminders in each chapter, sections 6.1, 6.3.3, and 6.4 discuss the implications of this approach in more detail. These sections also discuss the losses and conversion efficiencies of the feedstocks and explicitly point out that a “billion tons” in the reports do not represent a “billion tons” at the biorefinery throat; however, the actual number would be dependent on many variables. As an illustration of these losses, Figures 6.1 and 6.2 describe the potential biomass levels translated to usable energy (e.g. billion gallons per year and billion kilowatt hours) assuming losses of 20% in the storage and handling process (see footnote 67) and uniform conversion efficiencies (see Section 6.1 for more information and citations).
Although determining “total” cost is beyond the scope of the study, a hope is that the public KDF website will be a place where calculations of general “total cost” estimates can be shared. The KDF may also allow users to incorporate their own data and assumptions on losses and added costs in the future.
The benefit of the 2011 analysis approach is that it utilizes a uniform methodology to estimate national biomass supply at the farmgate or roadside at various market prices. These supply levels can be used to estimate costs for region- and site-specific logistics operations that would be needed to support the use of biomass resources with specific facility feedstock quality characteristics.
First, the MYPP used a cost-minimization approach to meet EISA RFS2 demand and projected biopower demand. The BT2 report uses a profit-maximization approach to identify the gross supply. Second, the MYPP considered grower payment as cost of biomass, which is farmgate price minus harvest cost (on a per ton basis). Comparing the results of the two reports would require adding harvest costs to the grower payments of the MYPP results to get a farmgate price. Finally, the MYPP results show increasing farmgate prices over time as demand increases for biomass. The BT2 projections assume a constant nominal price throughout the forecasted period.
There are two drivers assumed in the high-yield scenario that lead to increased production of agricultural residues. First, the high-yield scenario imposes aggressive yield growth of traditional crops in the forecast period (in 2030, the national average yield of corn increases to 265 bu/ac). This allows for more material to become available (the stover to grain ratio is 1:1). Second, the high-yield scenario relaxes the tillage choice constraint so that more acres move into no-till adoption. With no-till production, less residue is needed to maintain soil quality so more residue may be removed from fields.
The analysis in the 2005 Billion Ton Study was based on the assumption that sufficient agricultural and forestry residues would be left on-site to protect the soil from erosion and maintain soil productivity, or that producers would replace lost nutrients with fertilizer. The updated Billion Ton Study addresses more recent concerns over maintaining soil carbon. For corn stover, a new retention tool was developed to use site and weather parameters to estimate the retention levels that should protect soil from erosion and ensure long-term productivity and soil carbon.
The assumptions used are as important if not more important that the data and analyses. That is why we took special care to be transparent and clearly state these in the report. An appendix is provided that outlines all the assumptions. More importantly, assumptions were discussed among the contributors to develop consensus based on the best available information. Where possible, scenarios were used in such a way as to limit dependence on a single specific assumption, such as energy crop yields. Unfortunately, we were not able to complete full sensitivity analyses of the assumptions, but future studies could follow up on that issue.
14. The supply projections assume that land is shifting from potential food production to biomass production. "Under baseline assumptions, up to 22 million acres of cropland and 41 million acres of pastureland shift into energy crops by 2030 at a simulated farmgate price of $60 per dry ton."
True, there is a shift in land that could “potentially produce food” to biomass production. However, using the POLYSYS model, the demand for food, forage, and export (based on USDA's long-term projections and our extrapolations) are still met. This is accomplished by the following:
a) Over the projection period, the yields for the commodity crops (corn, soybean, etc.) increase (dependent on the scenario) which frees up land for energy crops while still meeting commodity demands. Projected yield increases in the baseline scenario are consistent with USDA long-term projections.
b) Economics drive land-use decisions for commodity and energy crops, so when biomass prices increase, it should free up more cropland and pasture land for energy crops. Idle land may also go into use to grow energy crops.
c) Finally, there are other factors assumed in the study that would make more land available for energy crops while still meeting commodity demands. A major one is the assumption that pastureland could be used more intensely. The study model assumes that improvements could boost production, such as the use of more fertilizer and the establishment of improved grasses to produce more forage per acre. Others factors that could increase available land include changes in tillage practices and livestock production.
These potential shifts are explored in further depth in the report, and a fact sheet was developed to help readers understand the assumptions, implications, and modeling of land-use change.
The fuel treatments are characterized as "integrated thinnings" in the report, with the assumption that the biomass will be removed along with merchantable products such as pulpwood and sawtimber. The model makes several other assumptions that restrict the removal of these thinnings: the harvest levels cannot exceed the growth in a state; there has to be mill capacity in the state for the merchantable products harvested; and only 50% of the thinnings are counted in the total as there would need to be a transition from the use of the conventional harvesting practice in which residues are left on-site, to integrated harvesting in which the biomass is removed with the marketable products. Finally, the report assumes that an uneven-aged prescription (i.e., only partial removal of tree stands across all diameter classes) with a 30-year assumed interval between thinnings. That would ensure the re-growth of the stands for a sustainable flow of merchantable products and biomass in the future.