The domestic political economy influences the degree to which social sustainability can be implemented. As seen in the case of land grabs, which are often done for biomass production for fuels [23, 31, 32], national governments will often make deals that ignore local and customary land rights. Bartley [10] points to several key factors. Firstly, the nature of the relationships between the business and state will impact the readiness of firms to see value in quickly shifting to sustainability standards. Secondly, the clarity of legitimacy of property rights and their administration will affect the harmonization of domestic con­ditions with transnational regulations. Thirdly, the nature of the national political regime and its openness to non-business agendas will influence the incentives for international and domestic actors to pursue private arenas of rule-making in that context. These three areas of consideration highlight why vast differences may exist in the conceptualization of sus­tainability standards in the affluent democracies of Europe and North America compared to the on-the-ground implementation of sustainability standards in developing countries [10].

Not only do national political economies matter but the actors embedded within those contexts significantly influence the shape of transnational governance mechanisms. As Geisler [33] points out, on the African continent African governments and elites subordinate African needs to offshore interests. For example, in Mozambique the production of biofuels has resulted in poorer groups losing access to the land on which they depend, with major negative effects not only on local food security but also on the economic, social and cultural dimensions of land use, in part because of the late implementation of planning and monitoring tools to ensure social sustainability [34].

The emergence and adoption of multiple, dynamic sustainability standards is influenced by key initiators and stakeholders such as TNCs, NGOs, development agencies, and oth­ers. The position of the standard-setters and adopters within global value chains, national business and institutional contexts brings greater understanding to the proliferation and convergence of diverse sustainability standards, how multiple actors in value chains influ­ence the proliferation, variation, and evolution of sustainability standards within a certain industry [35]. Firstly, leading buyers, by responding to their target consumers, affect the transmission of selection of sustainability standards in producer countries through the com­munication of preferences to suppliers. Secondly, producer size and type differentiate the types of standards adopted in a particular country. Thirdly, national exporters and traders play an important role in transmitting standards on behalf of clients through facilitating and overseeing the process of implementation and certification.

Feller-bunchers are similar to single grip-harvesters, but have the additional capacity to hold stems while additional felling cuts are made. The development of hydraulic accumulator arms that act like mechanical fingers on the felling head gives these machines the ability to hold one or more stems in place while a second or third is cut. Furthermore, this gives feller-bunchers the capacity to pre-brunch stems for a skidding or forwarding machine, without stopping harvesting.

14.6.3 Short-Rotation Woody Crop Harvesters

Short rotation woody crop harvesters, also called swath harvesters, are forage harvesters that are modified to harvest small diameter woody energy crops. These machines are typically able to harvest stems less than five inches in diameter. Stems are harvested and chipped, ground, or shredded, and fed through an auger to a trailer that is either pulled by the harvester or pulled by a second tractor driving in parallel.

Another type of risk faced by farmers is the risk that there may be no place to sell their crop once it is harvested. The farmers are then forced to pay substantial transportation costs to deliver to a distant market or they may have no outlet at all for a very specialized crop. The term ‘thin markets’ is used to describe the case where there are few buyers or few sellers. Two problems arise from thin markets. Firstly, there may be no one willing to buy or no one willing to sell at various times, such that both sellers and buyers may incur additional costs. Secondly, the loss of a buyer or seller due to financial failure or other causes may impose severe losses on other sellers or buyers. Such risks must be overcome when new markets are being established, as in the case of cellulosic feedstocks.

Douglas L. Karlen1, Marcelo Valadares Galdos2,

Sarita Candida Rabelo2, Henrique Continho Junqueira Franco2,
Antonio Bonomi2, Jihong Li3, Shi-Zhong Li3,

Jaya Shankar Tumuluru4, and Leslie Ovard4

INational Laboratory for Agriculture and the Environment, USDA Agricultural
Research Service, U. S.A.

2Brazilian Bioethanol Science and Technology Laboratory (CTBE)/Brazilian Center of Research in
Energy and Materials (CNPEM), Brazil

3MOST-USDA Joint Research Center for Biofuels, Institute of New Energy Technology,
Tsinghua University, China

4Biofuels and Renewable Energy Technologies, Idaho National Laboratory, U. S.A.

18.4 Overview

Plant biomass has been recognized globally as an important link to a sustainable energy future because it can be grown universally and converted into liquid transportation fuels or other material through biochemical, thermochemical, or catalytic conversion processes. However, those potential benefits must be viewed in the context of other global societal needs (i. e., food, feed, fiber, potable water, carbon storage in ecosystems, and preservation of native habitats and biodiversity) that must also be met by plant biomass growing on a finite amount of arable land. The development of cellulosic feedstocks for biofuels and other bioproducts must be accomplished in an economically viable, environmentally benign, and socially sustainable manner. This task is feasible throughout the world, as illustrated by examples from Brazil, China, and India.

Cellulosic Energy Cropping Systems, First Edition. Edited by Douglas L. Karlen. © 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

In Brazil, the primary cellulosic feedstock will be the straw and bagasse from the sugarcane industry. Traditionally, the straw was burned prior to harvest but increasing public concern has resulted in a phasing out of burning throughout the main sugarcane-growing regions of the country. Efforts to develop economically viable second generation ethanol production using these materials have been supported by investments from the Brazilian government through new research institutions, such as the Brazilian Bioethanol Science and Technology Laboratory (CTBE) and Embrapa Agroenergy. National and state research funding agencies as well as the Brazilian Bank for Economic and Social Development have also provided support for these endeavors.

In China, mandates that bioenergy production must not compete with food or feed production and must not inflict harm on the environment are key drivers in the development of this new industry. Crop residues and some plantation agriculture on marginal land are being explored but currently sweet sorghum has been identified as the best candidate for biofuel production. Similarly, in India, where 70% of the population depends on agriculture for its livelihood, bioenergy production must not have any negative impacts on food supplies or the overall economic welfare of Indians.

Undoubtedly, many similar and perhaps some divergent examples could be given by including perspectives from other countries, but that was beyond the scope of this book. The important perspective from this work is to recognize that Cellulosic Bioenergy Cropping Systems have both universal and site-specific characteristics that need to be fully vetted and understood to have truly sustainable food, feed, fiber, and fuel production throughout the world.

13.7.1 Modulization of Bales

Individual handling of bales (round or square) is not cost effective; it takes too long to load and unload the truck. Several concepts for a multibale handling unit are under development, and much of this development is still proprietary.

Permission was received to present a concept that was far enough along in development that second-year field tests were carried out in the 2012 fall-winter harvest season. The concept was developed by a consortium led by FDC Enterprises (K. Comer, personal communication) and is shown in Figure 13.9.

The self-loading trailer loads six stacks of six bales, referred to as “six-packs”, for a total load of 36 large rectangular bales (3 x 4 x 8 ft). The length of the load is 6 x 8 = 48 ft and the height is 3 x 3 = 9 ft. The width is 2 x 4 = 8 ft. The trailer built to implement the concept (Gary Kelderman, personal communication) is shown in Figure 13.10. Estimated load time is 5 min, about the same load time as the cotton module shown in Figure 13.2. In fact, the multibale unit emulates the cotton module system. The 36-bale unit can be

off-loaded by the truck directly onto the conveyor into a bioenergy plant, or it can be set on the ground in at-plant storage to be used later, just as is done with cotton modules at a cotton gin.

Among thermal pretreatment options, torrefaction, or pyrolysis of biomass in the 200- 300°C temperature range, is closest to widespread commercial use [8]. Torrefaction produces a devolitalized, hydrophobic, high-carbon content product often referred to as torrefied wood. Several characteristics of torrefied wood make it more efficient to transport and store than untreated biomass, including lower water and oxygen content, higher energy density, hydrophobicity, resistance to decay, grindability, and relatively homogenous parti­cle size. Torrefied wood is generally considered a solid fuel product suitable for combustion applications, including utility boilers and co-flring with coal, but may also be used in gasi­fication and bioproducts manufacturing. Much attention has been paid to using torrefied wood as raw material in the manufacture of fuel pellets because low water content and high energy density are desirable for most energy applications. The sequence of processing can also be reversed, with wood pellets serving as the feedstock for torrefaction. However, this configuration is not a viable in-woods option due to the difficulty in efficiently down­scaling pellet manufacturing, which is strongly subject to economies of scale in production, handling and transportation. In most torrefaction systems, once pyrolysis is initiated with an application of heat, the process is exothermic and self-sustaining, meaning the chem­ical reactions required to produce the end product will proceed without net additions of energy, such as heat from combustion of propane, natural gas or combustible gases pro­duced by the reaction itself. This provides a deployment advantage for log landings that are close to the harvest site and typically distant from infrastructure. Another advantage is that torrefied wood can typically be handled by the same equipment used to handle and trans­port processed biomass, though initial cooling and additional dust control measures may be required.

Pyrolysis of biomass at higher temperatures (300-700°C) produces recalcitrant charcoal as well as volatile gases, a fraction of which can be condensed into liquid pyrolysis oil, also called bio-oil. Mobile pyrolysis systems have been examined as a pretreatment option for woody biomass but are not yet widely used in the forest sector [9]. The charcoal produced has most of the same favorable properties as torrefied wood and can be used in its raw form as solid fuel or as a feedstock for the production of other products, including chemicals, pellets, activated carbon and soil additives. The charcoal output of pyrolysis of biomass is commonly called biochar when it is used as an additive to improve the bulk density and nutrient and water holding capacity of soils. Pyrolysis oil can be used in its raw form as liquid fuel. However, because of its high oxygen and water content and low chemical stability, it is generally considered a crude product to be used in the production of refined (i. e., upgraded) biofuels and industrial chemicals.

Pyrolysis in this temperature range often produces residual tars, which can provide fuel for conversion, be sold as a commercial output, or handled as an undesirable waste by-product, depending on production objectives, equipment capabilities, and markets. Sys­tems operating at the low end of this temperature range may be exothermic, similar to torrefaction systems, but fast pyrolysis units operating at higher temperatures are charac­teristically endothermic and require net additions of energy to sustain the thermochemical reaction due to their high heating rate and the relatively short residence time of the feed­stock. Often this energy can be provided by combustion of producer gas generated by the system, which is generally composed of carbon monoxide, hydrogen, carbon diox­ide, methane and other non-condensable gases. Because of the high temperatures and smaller feedstock particle size, which facilitate rapid heat transfer, the pulverized char­coal from fast pyrolysis systems can require significantly different handling than wood chips or torrefied wood — most often a cooling phase followed by containerization in drums, closed trailers, or large industrial bulk bags. Compared to biomass, pyrolysis oil is energy dense, and thus has the potential to improve transportation efficiency, but as a liquid product it adds material handing requirements that are unusual for most forest oper­ations, including on-site liquid fuel storage, specialized trucking needs, and fire and spill containment preparations.

14.8.2 Locating Pretreatment Operations

As a component of woody biomass logistics, pretreatment can occur close to the harvest site, at intermediate processing and storage facilities such as concentration yards, or prior to use at the conversion facility. The location and timing of necessary pretreatment is highly dependent upon the end use and other components of the supply chain. However, several general considerations are worth mentioning here. In any logistics configuration, the value of pretreatment is likely to depend on the cost of the pretreatment weighted against the cost savings associated with increased transportation efficiency and the difference in delivered price between the treated and untreated materials. For example, when compared to green chips, torrefied wood produced from green chips at a harvest site may be cheaper to deliver on a cost per ton basis and may also command a higher delivered price attributable to its higher energy content. However, if the cost of the torrefaction operation is greater than the sum of transportation cost savings and new revenue, then the torrefaction preprocessing option is unlikely to be commercially viable.

Balancing the scale of operations is also important. Many existing pyrolysis and tor — refaction technologies that can be deployed to forest settings have much lower material throughput (e. g., 1 t h-1) than grinding and chipping systems, which can produce up to 50 th-1. When forest operations are bottlenecked through lower productivity preprocessing, gains in transportation and revenue may be erased by operational delays in the harvest­ing and processing components of the system. This is especially true of batch systems, where equipment may be idle during preprocessing periods. In addition, some technologies (e. g., refinery operations) benefit from clear economies of scale and cannot be effectively down-scaled for deployment to in-woods and concentration yard environments. Many of these challenges can be overcome with effective engineering, operations planning and logistics management, but others reflect the realities of preprocessing technology deployed in difficult operating environments.

Large scale expansion of crop production for bioenergy would lead to a large increase in the amount of transpired water that is used for human purposes, perhaps equaling the present amount used by the end of the twenty-first century [29]. Globally, commercial bioenergy production is projected to consume 18-46% of the current agricultural use of water by the year 2050 [29]. Increased bioenergy production will strain water resources in all continents but the challenges will be most pronounced in Asia and Africa [30]. By 2075, water use for the production of bioenergy could push some important agricultural countries, including the United States and Argentina, from a condition of no water stress into a condition of incipient national water stress [29]. U. S. agriculture uses both blue water (water from aquifers and surface supplies) and green water (water stored in soil transpired by plants) [31]. U. S. agriculture is the second largest consumer of blue water [32,33] and it, along with forestry, are the major industries using green water. The supply of blue water is dependent on effective precipitation (EP), which is defined as the part of rainfall that reaches streams or recharges groundwater. The future biofuels production industry will create major new demands on the quantity of water used by agriculture and production forestry in the United States. New research and new tools are needed to account for these water demands as the nation implements sustainable biofuels production, because in many parts of the United States the agricultural sector already face water shortages. In the west, agricultural withdrawals account for 65-85% of total water withdrawals [33]. In the east, irrigation supplies are under pressure from competing uses, especially in periods of drought. Although overall water withdrawals in the United States have decreased since 1980 and irrigation efficiency improvements are still possible, the amount of both green and blue water needed for a biofuels-based energy supply is much greater than for the historic, fossil fuels based economy.

Comparisons of perennial bioenergy crops (both woody and herbaceous) have shown higher evapotranspiration (ET) and less EP than either annual crops or natural ecosystems. Simulations using the Environmental Policy Integrated Climate (EPIC) model showed the potential for 12-30% more ET from switchgrass than either corn or winter wheat in the Midwest [34]. Water balance measurements for pine plantations in the southeast showed 30% higher ET than natural pine forests [35]. At this point, watershed research has not shown that these increases in field scale ET will affect streamflow discharge for areas of perennial bioenergy crops expected in most watersheds. Modeling studies have examined the effects of conversion to perennial bioenergy crops, especially switchgrass, on water quantity and quality.

Simulations using the Soil and Water Assessment Tool (SWAT) in Minnesota showed only a small decrease in streamflow when 27% of the watershed was put into switchgrass instead of conventional crops [36]. Conversely, applying SWAT to the Delaware river watershed in Kansas and assuming 43% of the watershed was converted to switchgrass estimated that surface runoff would decline by 55% with large reductions in edge of field erosion, sediment yield, and nitrogen export. Reduction in nitrogen export depended on the fertilizer level assumed for the switchgrass [37]. Modeled results from the United Kingdom showed that EP was lower for both Miscanthus x giganteus (M. x giganteus) and short-rotation coppice (SRC) willow (Salix spp) [26]. The decrease was greater for SRC willow than for M. x giganteus, generally reflecting the lower water use efficiency in C3 plants (willow) than in C4 plants (M. x giganteus). On a watershed basis, the effects on EP will depend on both the fraction of the watershed in perennial biofuels crops and the precipitation. Modeled decreases in EP were greatest in areas below about 600 mm annual precipitation [26].

Vanloocke et al. [38] used a plant growth and ET model to estimate that M. x giganteus grown in the Midwest United States would use more water than the agro-ecosystems it might replace. The model showed that substantial increases in water evaporated to the atmosphere and potential decrease in EP to streams and groundwater would only occur when the M. x giganteus fraction cover for a watershed exceeded 25% in dry regions and 50% in nearly all of the rest of the Midwest. Conversion to woody biomass may also lead to reduced streamflow compared to non-forested watersheds. Farley et al. 2005[39] estimated that in arid areas where streamflow was 10% or less of rainfall, afforestation could eliminate most streamflow and that in areas where streamflow was 30% of rainfall, streamflow could be cut in half by afforestation of shrublands or grasslands.

Direct measurements of water quantity and quality effects of perennial biomass grasses are rare. McIsaac et al. [40] showed that nitrate leaching was very low beneath unfertilized M. x giganteus and switchgrass primarily because drainage water was reduced, especially under M. x giganteus. They estimated that in the tile-drained Midwest, M. x giganteus could reduce streamflow by as much as 32% compared to conventional corn/soybean rota­tions. Experimental studies of bioenergy feedstock crops generally give results that show the complex interactions among fertilizer regimes, crops, and development of perennial crop­ping systems. For instance, in north Alabama, coppiced sweet gum had much lower nitrogen and phophorus losses in runoff than corn, but switchgrass had phosphorus losses similar to corn and only in the final two years of a five-year trial were NO3-N losses lower [23]. In addition, there were high erosion losses for sweet gum unless it was grown with a cover crop.

Although runoff and erosion should be less from fields in perennial bioenergy crops than in annual crops, meaningful comparisons will depend on management of both cropping systems. Conservation tillage generally reduces runoff and erosion and may have lower rates than under perennial crops, especially during the establishment phase of the bioenergy crops. Furthermore, the high cost of perennials may lead to low establishment rates and more bare soil than with annual cropping systems.

Sustainability issues related to water will help determine the types of cellulosic feedstocks grown. For instance, due to higher biomass production, greater leaf area index, and longer vegetative growing season, M. x giganteus requires more water during the growing season than switchgrass or corn [40, 41]. Consequently, water availability strongly influences M. x giganteus yields, and the crop is thought to be best suited to locations that receive at least 30 inches of precipitation per year. In contrast to M. x giganteus, switchgrass yields are most strongly influenced by nitrogen availability [42]. This means that in areas like the Midwest where rainfall is generally adequate, but high nitrates in drain tile are an issue, M. x giganteus would be a better choice for producers than switchgrass. In drier areas of the country, where water is limiting, but groundwater quality is not an issue, adequately fertilized (i. e., 50-100 lbN/acre or 56-110 kgN/ha) switchgrass may produce higher amounts of biomass [42].

It is necessary to give the reader some additional perspective on SSL operations. If the yield of switchgrass in a commercial-scale operation averages 4 ton/acre, this equates to approximately 9 bales/acre. It is specified for this example that the minimum size SSL is 60 acres = 540 bales, and the maximum size SSL stores 1200 acres = 10 800 bales. If 70% of the theoretical loading of 30 racks/d is achieved, the contactor will load 21 racks x 16 bales/rack = 336 bales/d. The minimum size SSL will be loaded out in about 540/336 = 1.6 days. The maximum size SSL will be loaded out in /10 800/336 = 32 days.

Cost of the SSL operations at the smaller SSLs will be higher because of the mobilization charge to move equipment in for a relatively few days of operation. It is probable that the load-haul contract offered by the plant for each individual SSL will consider both the haul distance and SSL size, thus the per-ton payment will be different for each SSL.

B.3 Total Trucks Required — 24-h Hauling

To achieve 24-h hauling, the truck drivers will work 8-h shifts and the trucks will run continuously from 0600 Monday to 0600 Sunday, a total of 144 h/wk. The total racks processed each week is 630, equal to 315 truckloads. If a uniform delivery is assumed, the average truck unload time is

315 trucks/144 h = 2.2 trucks/h

or about one truck every 27 min. This productivity is well within the Rack System design goal of a 10-min unload time.

As previously stated, the 24-h hauling concept envisions that the loading crew will leave a supply of loaded racks on trailers at the SSL when they finish their 10-h workday. These racks will be hauled during the night. The next morning the loading crew will go to work on the trailers with empty racks delivered during the night and fill them during their workday.

The key variable in hauling is the truck cycle time. To calculate cycle time for this example, we need an average haul distance. An actual database was developed for a proposed bioenergy plant location at Gretna, Virginia and was used to calculate an average haul distance.

An analysis was done for a 30-mile radius around Gretna to identify potential production fields based on current land use determined from current aerial photography. Using a conservative assumption, about 5% of the total land base could be attracted into switchgrass production. SSLs were established at 199 locations (Figure 13.11), and the existing road network was used to determine the travel distance from each SSL to the proposed plant location at Gretna. Some loads were hauled two miles and some were hauled over 40 miles. A weighted ton-mile parameter was computed and found to be 25.4 miles. This means that, averaged across all 199 SSLs, each ton travels 25.4 miles to get to the plant.

Truck cycle time is calculated using the 25.4-mile average haul distance, a 45 mile/h average speed, 10-min load time, and 10-min unload time. Theoretical cycle time is 1.46 h. In 24 hours of operation, one truck can haul

16.4 loads per truck per day

Assuming that a truck can average 70 % of the theoretical capacity, the analysis uses 0.7 x 16.4 = 11.5 loads per truck per day. Remember, since the trucks run continuously, a decimal number of loads can be used as the average achieved per-day productivity.

It is not practical to use the each-contractor-runs-their-own-trucks assumption for 24-h hauling. The way to maximize truck productivity is to have the Feedstock Manager be able to send any truck to any SSL where a trailer with full racks is available. This greatly facilitates the hauling at both day-haul and night-haul SSLs.

Total trucks being controlled by the Feedstock Manager are:

53 loads/d required at the plant/ 11.5 loads per truck = 4.6 trucks

= 5 trucks

B.4 Total Racks Required — 24-h Hauling

Since the only time deliveries are not being made is the 24-h period, 0600 Sunday to 0600 Monday, the amount in at-plant storage can be reduced. It was decided to use 1.5 days as the minimum at-plant storage, so the total hours of capacity required in at-plant storage at 0600 Sunday, when deliveries are ended for the week, is:

24 h (actual) + 1.5 d x 24 h/d (at-plant storage) = 60 h

3.75 racks/h x 60 h = 225 racks

Total trailers are calculated as follows. Each truck has one trailer connected, two parked at a “day-haul” SSL and nine parked at a “night-haul” SSL for a total of 12 trailers. The total racks on trailers is calculated as follows:

5 trucks x 12 trailers per truck x 2 racks/trailer = 120 racks

Ostensibly, total racks required is calculated as follows:

At-plant + On 60 trailers + Reserve = Total 225 + 120 + 5 = 350

The actual number of racks required is calculated by subtracting the racks on parked trailers from the rack total (empty + loaded) at the plant. Potentially, 60 loaded trailers can be parked at the plant when hauling ends for the week at 0600 Sunday. In order for this procedure to work, the racks on most of these 60 trailers have to be returned to SSLs during the period 0600 Sunday to 0600 Monday so that they will be in position for operations to begin at each SSL at 0600 Monday. This requires some empty back hauls. Cost for these empty back hauls is a level of detail that must wait for a more sophisticated analysis.

When racks on trailers are counted as part of the at-plant storage, the minimum number of racks is:

At-plant + On 60 trailers + Reserve = Total (225 — 120) + 120 + 5 = 230 Average number of cycles per rack is

29 610 racks processed per year/230 = 129 cycles/y,

or about 2.7 cycles per week for 47 weeks of annual operation.

Costs and revenues for perennial and multiseason crops occur over several seasons so addi­tional calculations are needed to represent annual costs and returns. A separate enterprise budget is prepared for the establishment period of the crop. The establishment period may be one or more seasons, during which the crop is planted and allowed to grow to sufficient maturity that harvesting can begin. Total cost minus any revenues during the establishment period is calculated. The net cost of establishment is then amortized as an annual expense over the productive period of the crop. North Carolina State University (NCSU) [2] provides an example of an enterprise budget for switchgrass, including an establishment budget and a line on the annual budget listing amortized establishment cost. A life cycle accounting approach may be applied to perennial or multiseason crops such that costs or benefits of restoring land to its original productive state can be assessed and distributed backwards on an annual basis to the crop.

Roundtables are a type of multistakeholder partnership for sustainability standard-setting that has gained prominence in recent years. As a specific form of private governance, such collaborations focus on improving sustainability within one specific commodity chain or sector. As with other multistakeholder partnerships, roundtables include actors from

private businesses as well as NGOs. Representatives from government agencies might participate by consulting and observing, but have no decision-making role. Roundtables go beyond merely creating niche markets and instead aim to transform entire commodity chains towards more sustainable practices. The current generation of roundtables — such as Roundtable on Sustainable Palm Oil (RSPO), Round Table for Responsible Soy (RTRS), Better Cotton Initiative (BCI), Better Sugarcane Initiative (BSI) and Roundtable for Sus­tainable Biofuels (RSB) — trace their conceptual origins to the multistakeholder initiatives of the forest and marine stewardship councils (FSC and MSC) [28]. Roundtables connect commodity chain actors from around the globe. These actors come from diverse locations, occupy various roles within the commodity chain, and hold different belief systems regard­ing sustainability. The legitimacy of their collective actions is based on the justification for why they are the right actors to govern the commodity chain, and the creation of a common understanding about what and how they desire to govern [28]. The establishment of shared goals and common activities are the basis for the working relationship.