During the spring and summer of 2010, the University of Georgia (UGA) assessed the state of biomass harvesting, collection, and transportation technology in use across the United States' six forested regions through a literature review, on-line surveys of biomass market participants, and a series of one-week field visits by research team members.
The UGA team's final conclusions are a component of the Wood Supply Research Institute's recently concluded Forest Biomass Supply Chain project, which combines this team's operational report with the consultant FORISK's study of inventory and demand trends to produce a multi-lateral and cross-regional view of trends, limitations, and key success determiners for a developing forest biomass supply industry.
Biomass harvesting systems differ by region, largely due to the size and strength of regional pulpwood markets and dominant forest species. Regions with significant hardwood resources and historically weaker pulpwood markets typically leave larger volumes of biomass after roundwood harvests with larger residual piece sizes. In these regions "cold" biomass harvesting systems typically follow roundwood systems to chip or grind piled residues. In the South Central and Southeast regions, with more competitive pulpwood markets that rely more heavily on planted pines, lower per-acre residue volumes remain, with smaller average piece sizes leading to greater issues with ash content in fuels. "Hot" systems that chip or grind alongside or instead of roundwood systems are more common in these regions. The relatively low density and value of biomass forces contractors everywhere to focus intently on improving transportation efficiency. While most forest biomass is destined for markets that will combust it to generate heat or electricity, today only markets in the West routinely buy biomass on a dry-weight basis. Other regions may adopt this practice in the future, as it creates incentives across the supply chain to improve the net energy content of delivered fuels.
With the permission of WSRI, FRA is pleased to offer this overview of the UGA team's operational observations. As WSRI Executive Director Jim Fendig notes in his column in this issue, we hope to provide additional insights from this important project in the form of Technical Releases throughout this year. Please contact the authors care of Dale Greene, This e-mail address is being protected from spambots. You need JavaScript enabled to view it , 706-542-6652.
South Central
Most biomass crews in Arkansas, Louisiana, and eastern Texas are early adopters, although generally with three years or less chipping experience. Biomass capacity in the region can be increased by expanding the trucking capacity of existing crews, adding additional crews, or adding chippers to roundwood operations. Contractors were more successful during the BCAP program's preliminary run but were suffering following its suspension. Mills reduced their delivered prices during the program but did not return them to prior levels once it was suspended.
Contractors frequently cited unloading times at fuel purchasing plants as a limiting factor to productivity. Chip dumps can become de facto production quotas, due to long turnaround times in the middle of the day. While relatively few contractors were producing biomass at the time of the study, supply still appeared to outpace demand in this region. The ability to leave clean harvest sites provided a substantial procurement advantage to many who had months of work booked, as evidence. This factor is perhaps more important than potential revenue. With additional markets or stronger pricing, most would expand their chipping capacity.
Our South Central field visits did not include any in-woods grinders, and only a few markets accepted grinder feedstocks. However, a new electric power plant in Lufkin, Texas has given rise to eight grinding crews that currently sell boiler fuel into pulp markets. The power plant intended to use in-woods grindings following its planned startup in December 2010. An in-woods slash bundler has also been employed to provide storable slash feedstock by drying slash bundles for up to nine months.
All contractors were conscious of the moisture content of the material they produced, although it was not a factor in their compensation. Chipping contractors all claimed low ash contents and stated that mills all threaten refusal of high-ash feedstocks, a key reason they use chippers and focus on green material.
Low production was characteristic, with daily production targets between 4 and 6 loads using 400-600 hp chippers. Most contractors claimed this operating rate was sufficient to be profitable but were willing to increase production should markets improve. By contrast, some had reduced chipping production by parking chippers in the face of poor markets. No crews used more than three trucks to deliver biomass chips. Most contractors preferred live-bottom trailers to avoid delays at truck dumps, although few actually owned them, due to the higher purchase price and the current soft markets.
Most operators either chipped before or after roundwood harvest to capture unmerchantable stems or in association with precommercial thinning. Concurrent chipping with roundwood operations was less common. Contractors reported paying stumpage to landowners for harvested fuelwood, although such arrangements varied depending on the conditions of the harvest.
Appalachians
Wood biomass markets in the Appalachian region (Virginia, Tennessee, West Virginia, and Ohio) are not firmly established. Many existing markets rely heavily on mill residues. Harvesting contractors either are in close proximity to wood-to-electricity facilities, or they supply pulp mills with both roundwood and biomass chips. Contractors address logistical challenges with the Appalachian terrain by greater use of level-swing, tracked feller-bunchers and grapple skidders. The steepest areas of Appalachia have little biomass harvesting due to an inability to get low-value, woody materials roadside economically. Road networks in the area are often designed with straight-frame trucks in mind, posing problems for chip vans due to steep grades and tight curves on forest roads.
Pulpwood markets are less common in the Appalachian region than elsewhere; thus, substantial volumes of lower-quality, pulpwood-sized material often remain on harvested sites. This situation offers potential biomass production if the logistical roadblocks can be overcome. Most crews we visited had only one market for biomass, with haul distances ranging from 30 to 130 miles.
Hardwood residues lend themselves to processing by chippers rather than grinders. The size of materials cut from hardwood roundwood stems and the propensity for hardwoods to "fluff" in a grinder (making it difficult to achieve full payloads) support this decision. Most operations were using larger chippers (600+ HP) concurrent with the harvest of traditional products. The volumes of residue generated from hardwood stems required a concurrent biomass operation because landings were not large enough to store all of the biomass produced. Roundwood-to-biomass ratios of three to one were common on the low end, but contractors claimed that on lower-quality sites it was not uncommon to see ratios of one to three. Reported fuel consumption of the chipper or grinder ranged from 0.3 to 0.6 gallons of diesel per ton of chips or grindings. Production averaged three loads per day of biomass, but sites with higher biomass-to-roundwood ratios could support 6 to 8 loads per day. Because most biomass operations were run concurrently with the harvest of traditional products, loggers did not target a minimum volume of biomass. Most sought at least 20 acres for their crews, although some contractors were willing and able to pursue smaller tracts as necessary.
Lake States
Wood biomass markets in the Lake States (Michigan, Minnesota, and Wisconsin) have existed for as many as 20 years. Delivered prices are clearly higher for biomass in this area, as average haul distances exceeding 80 miles are common, and reported maximum haul distances approach 200 miles.
Cut-to-length logging has broad use across the region, with 100-inch roundwood markets still common. CTL presents a challenge for biomass recovery, due to dispersion of limbs and slash across the site. Biomass contractors that follow CTL operations typically forward slash to horizontal grinders at roadside that reduce the slash and load it into open-top trailers. Approaches to delimbing and the timing of forwarding vary. Some contractors grind "hot" and forward slash to roadside while the grinder is on site. In such cases, the forwarders are a necessary part of the grinding operation. "Cold" operations forward slash as a part of the roundwood harvest, creating large roadside piles for the follow-on grinder operation. This approach adds the cost of slash forwarding to the roundwood harvesting crew while minimizing operational delays for the grinding operation.
Contractors in some areas use tree-length skidding. Whole-trees are either bucked with slashers at roadside or are fed directly into whole-tree chippers. When clean chippers are used, the residue is fed into horizontal grinders. When roundwood is harvested, intact tops are cut from stems and set aside to be fed into chippers.
Stand types vary widely across the area, but contractors specifically mentioned three stand types for biomass recovery. Mixed hardwood stands often produce roughly equal volumes of biomass and roundwood, due largely to the volume of unmerchantable stems fed to the chipper. Pine stands generally produce about one load of biomass for every three loads of roundwood. Pure aspen stands generate the highest-value pulpwood and are typically merchandised closely, thus leaving the fewest opportunities for biomass residues.
Grinding contractors are not reporting ash content issues, likely due to the use of forwarders in moving slash cleanly. Residue piles are rarely pushed with skidder blades, minimizing the addition of dirt. We also did not find any market preference for chips over ground slash. Quotas were rarely mentioned as a limiting factor in this area. While quotas fluctuate weekly by market, most operators reported multiple available biomass markets, enabling them to redirect supply to maintain production.
Under the federal Biomass Crop Assistance Program (BCAP), a number of new biomass contractors entered the industry, flooding many markets with material. The resulting downward pressure on biomass prices and tightening of quotas occurred during a very short winter break-up, leaving many markets full entering the summer. Experience with BCAP did indicate that stronger markets could bring more material to mills, but all interviewed contractors disliked it, as it had disrupted stable and mature markets, and stability had not yet returned following its suspension.
Northeast
Wood biomass markets in the Northeast (New Hamphire and Maine) have been well-established for a number of years, with pulp mills, wood-to-electricity plants, and smaller local heating plants all in the mix. Multiple markets have helped logging contractors maintain consistent production of high-quality biomass feedstock. The reliable demand from base-load electricity facilities provides a steady foundation for the market that is less affected by market shifts or seasonal factors. Increased demand for biomass during winter months from facilities generating heat and/or process steam typically align with preferred winter harvesting conditions and increased logging production. Facilities stockpile material during winter months to offset production limitations during spring break-up.
BCAP destabilized markets, with many facilities building large stockpiles of subsidized biomass in anticipation of the program's conclusion. This glut, combined with a mild winter break-up, left excess supply in the markets through summer and held delivered prices low. The consensus among most contractors was that markets had already incorporated biomass into their operations at a sustainable price, and the BCAP stimulus merely upset the market balance. In some instances, contractors used the additional revenue provided by BCAP funds to explore new harvesting opportunities such as biomass-only harvests for stand improvement, but such operations were the exception rather than the rule.
Tree-length logging predominates in the Northeast, though cut-to-length operations also exist, particularly on smaller tracts. Most contractors are using a cold logging approach that decouples the trucking from the harvesting operation. Stems are delimbed and stacked at roadside, typically with stroke delimbers. Tops are left intact when possible and piled separately. Operators stack biomass materials in well-organized, linear stacks to facilitate chipping and minimize soil contamination. Smaller limbs that have been removed by stroke delimbers are typically returned to the stand and placed in skid trails. This practice keeps biomass cleaner while adding protection to trails on weaker soils. Biomass typically represents between one-quarter and one-third of total harvested volumes, but many contractors stated that this proportion would vary with the strength of pulpwood markets, indicating significant overlapping demand for these marginal trees.
Markets purchase on a green-ton basis, prompting contractors to try to process harvest residues within two weeks of harvest to minimize drying. Chippers are more common than grinders, due partly to the focus on green material, with disc chippers about as common as drum chippers. Biomass residues are often substantial, with intact tops and smaller stems the predominant components. Fuel consumption of chippers averages 0.35 gallons per ton, with the majority of contractors reporting average biomass production of 5 to 6 loads per day. Dirt and ash contents are reported at very low levels. Delivered moisture content averages 45% for hardwoods and 50+% for softwoods.
Trailer configurations are predominantly 45- to 48-foot dead-floor trailers. Walking floors are only common where smaller local seasonal heating markets are served. Payloads typically average 33 tons and range from 30 to 36 tons. Multiple markets help keep average haul distances around 30-50 miles.
West
Western (Washington and Oregon) biomass markets have existed for years, primarily for users in the forest products sector and a few wood-to-electricity power plants. A key difference in this region is the payment for biomass on a bone-dry ton basis. This approach changes operations significantly. We found highly productive contractors with typical daily production targets for grinding crews of 10+ truckloads.
Harvesting residues/slash from cable yarding and ground logging is abundant, with 30-50 tons per acre common. Biomass contractors ran stand-alone operations, grinding material 4 months to 3 years after harvest (25-45% moisture content). Grinders tended to be larger (800-1500 hp), consuming approximately 10 to 15 gallons per load, depending on the size of the grinder.
Biomass recovery provides landowners and forest managers with an alternative to burning as a means of reducing debris. Ideally, these activities take place pre-planting to increase plantable area. One forest manager reported recovering 2.5 acres on an 88-acre tract from grinding roadside slash piles. Other sources of biomass in the region include urban land clearing, prunings from fruit or nut orchards, and conversions of orchards to vineyards.
Coordination between logging and biomass activities is not common. Biomass operators often deploy equipment to pile logging debris and prepare landings or roads to maximize grinder utilization. Such steps increase daily grinding production by 3 or more truck loads a day, according to contractors.
One of the unique challenges in this region is terrain. Roads are steep with tight curves that force contractors to develop special transportation systems. Drop-belly trailers are standard region-wide. We observed two different strategies: using shorter trailers where access was difficult and modifying truck/trailer configurations. The use of 28-foot and 32-foot drop-belly trailers with a capacity of 15 to 18 tons helped access difficult slash pile locations. These short trailers were often used for woods roads travel then coupled into twin configurations with 32- to 35-ton payloads for highway transportation to end users.
Hermann Brothers Logging (Port Angeles, Washington) uses modified truck trailer configurations to handle the steep and difficult terrain on the Olympic Peninsula. Their 45-foot trailers have been fitted with remotely controlled trailer axles that can be steered to handle tight curves. Air suspension systems on the trailers can also increase ground clearance by up to six inches when needed.
Another contractor strategy to optimize hauling was the use of centralized receiving/reloading yards. JK Construction (Raymond, Washington) hauls slash in 40-foot dump trailers to a centralized location where it is ground and then reloaded into 48-foot trailers (35-ton payload) for delivery to end users. Hermann Brothers uses a yard to receive grindings from woods crews and then reloads the grindings into higher-capacity highway drop-belly trailers. These approaches allow for economical use of smaller trailers or heavier off-road trucks on challenging wood roads but maximize payloads for longer-distance deliveries on public roads.
In general, contractors had multiple markets for their feedstock, with at least three pulp mills in the region reported to be increasing wood biomass power generating capacity. Most operators considered the BCAP program a disruption to a market that was already stable and mature, distorting prices.
Southeast
The bio-energy industry in the Southeast is developing rapidly in some areas, with wood-to-electricity and pellet plants operating, under construction, and announced across the region. These opportunities are localized, and the harvesting workforce is cautiously optimistic about strong future biomass markets. Presently, chipping predominates, with biomass shipped mainly to pulp and paper facilities. Grinders are well adapted to process tree-length logging residues, and 80% of the region's production is tree-length processed at roadside. High ash content of grindings is limiting the growth of that form of feedstock, especially for wood pellet and direct combustion with older boiler technologies.
Most contractors produce material for one or two markets with quota limitations often preventing production at full capacity. Biomass production could be increased in the short-term by increasing the trucking capacity of existing crews, adding additional crews, or adding chippers to operations not currently using them. Issues with unloading times at some mature biomass markets (pulp mills) have multiplied in recent years with the growth of woods residues to meet higher biomass demand. Long lines and wait times in the middle of the day are not uncommon, as many mills continue to use older, slower unloading facilities for biomass deliveries.
A mixture of dedicated biomass chipping crews producing whole-tree chips and roundwood crews utilizing a smaller chipper to produce chips from roundwood residue are the principal operating configurations, though grinders are still in place where markets exist for the material. A push towards cleaner feedstocks has created interest in screening technologies to remove soil contaminants from woody biomass. Coastal areas, with high sand content, were leading this push, but the additional costs have led most contractors to switch to chippers. While many markets are showing interest in drier feedstocks for increased energy content, to date compensation is still based on delivered green tons.
While production quotas are often cited as a limitation, most crews target 8 to 10 loads of biomass per day from dedicated chipping or grinding crews. Integrated crews typically aim for much lower targets. Payloads normally range from 25 to 27 tons. Both live-bottom and dead-floor trailers are common; often both are used by a single crew to offer the flexibility of hauling occasional loads to facilities without truck dumps. BCAP payments aided contractors poised to take advantage of the biomass markets, as wood markets in general were relatively poor while BCAP was in effect.
Summary
We found biomass harvesting to be most developed in regions where pulpwood markets have historically been somewhat limited. In these regions, biomass markets have developed over the years to exploit this supply of unused or residual material economically. Expanding biomass harvesting in regions with stronger pulpwood markets (South Central and Southeast) will involve more competition with pulpwood, attempts to collect smaller residual material, or both. We found the use of larger-size materials that are typically piled by loaders or delimbers rarely to have ash-content problems. For that reason, grinding was often as acceptable as chipping in these regions.
Given the low density and low market value of biomass material, efficient trucking is of paramount importance. In all regions, we found extensive efforts to maximize truck payloads, limit hauling distances, and (to a lesser degree) reduce turn-around times at mills and in the woods. All are important keys to making trucking efficient.
Until liquid biofuel manufacturing establishes itself, it appears that forest biomass is predominantly directed to combustion. Reducing the moisture content of these fuels would significantly increase their energy content and market value. At present, payment for woody biomass on a dry basis is only standard in the West, but this approach creates incentives across the wood supply system to develop economical ways to increase energy content prior to delivery. In contrast, payment on a green-weight basis is common in all other regions and encourages delivery of material with high moisture content to maximize weight and revenue to the harvesting contractor. Resolving this issue will likely be important when biomass markets recognize the added value of drier and cleaner feedstock develop systems to base payments on such factors.
