Sustainably sourced biomass has an important role to play in climate change mitigation and adaptation strategies by providing a supply of renewable carbon to the economy. Stable and secure sustainable biomass supplies are needed for energy independence as well as for de-fossilizing the economy [1
]; in addition, de-fossilization driven by climate change mitigation strategies is expected to increase the demand for biomass further.
This higher demand is driven not only by combustion and combined heat and power (CHP) plants but by more sophisticated conversion streams [2
], highlighting the need for sustainable biomass assortments of consistent quality with easily controllable characteristics [3
]. Most biochemical producers relying on woody biomass require consistent high-quality feedstock; for example, biomass refinery plants using gasification and pyrolysis conversion technologies are more sensitive than traditional combustion plants to particle size, ash content, and moisture content [3
]. However, differences in biomass feedstock, as a result of local forest conditions, energy production traditions, and supply chains [5
], can influence the regional preferences of feedstock end-users.
At a regional level, logistic biohubs are increasingly being recognized as an important part of an efficient raw material supply chain for pulp, paper, and biomaterial industries [6
]. The business models for biohubs and their functionality depend greatly on, for example, the type, amount, and quality of industrial feedstock demand as key measures for optimizing raw material utilization [10
]. For the whole supply chain, from forest to final product, to work efficiently, a good understanding of suppliers’ capabilities and customers’ needs is also needed [13
All biomass conversion processes require comminution and some level of other pre-treatment, such as drying, sieving, etc. The quality of wood chips can be defined in the same way as pre-defined assortments such as wood pellets or energy wood by their moisture and ash content, type, particle size, and heating value [14
]. Inconsistencies in biomass quality between individual deliveries as well as between biomass suppliers cause the most problems for process control at facilities, even once they have been adjusted for specific biomass properties and their variation [15
]. On the supply side, handling a comminuted biomass of various particle sizes and moisture content has a considerable effect on biomass storage, drying, loss, and self-ignition [19
This highlights the need for a better understanding of how facilities perceive different aspects of pre-defined biomass assortments and specific biomass characteristics in order to streamline biomass supply and demand in regional biohubs. Key biomass characteristics include moisture content, particle size, and ash content [14
] as well as availability and supply [25
]. Depending on the biomass conversion process used, the requirements for specific biomass properties can vary; in general, large-scale, bubbling, fluidized bed boilers are the least sensitive to moisture content, ash and particle size, and variation compared with smaller grate-type boilers [26
The aim of this study was to describe and assess end-users’ preferences regarding biomass feedstock characteristics and to analyze the key factors that influence procurement. The goal was to determine end-users’ perceptions of different wood-based industrial facilities, rank the features of business models in terms of facility location, size, and biomass storage, handling, and procurement, and determine relative weights and ranking for biomass attributes based on the opinions of experienced professionals from bioenergy facilities across different countries.
The characteristics of biomass feedstocks are key factors that affect the decision-making process along the supply chain. This study analyzed the preferred biomass feedstock characteristics of professionals from a variety of bioenergy facilities. Four countries with significant bioenergy developments were included, representing a well-established bioenergy sector covering a wide range of conditions and technologies. Canada has some of the largest areas of forested land, with solid biofuels representing about 133 TWh, and it was the second-largest exporter of wood pellets in 2017, representing 11.9% of total global exports [31
]. Despite their smaller land areas, Finland and Sweden are pioneers in the use of advanced wood biofuels. In both these countries, bioenergy has become the largest energy source, surpassing oil, and wood fuels represent around 100 TWh and 140 TWh, respectively [32
]. They are world leaders in the use of solid biomass, with the highest per capita energy use [34
], and provide important regional biohubs in pellet production and consumption [35
]. In Australia, solid biofuels contribute 50 TWh to the country’s energy supply, which, compared with its area of forested land, indicates a large potential to increase over the next few years [36
The respondents represented a wide range of bioenergy facilities, including the most common biomass conversion technologies at the market level. For this type of study, the representativity and reliability of the results are linked to the selection and relevance of the respondents involved. The pool of potential respondents was chosen to include senior and experienced decision makers who could provide qualified assessments. However, as in any study based on surveys, there were obvious challenges and limitations: despite targeting a large data set of professionals, the response rate was lower than expected. The study was carried out during the coronavirus pandemic, when, globally, much work was carried out from home and access to field studies at industry sites was largely restricted. One of the most accessible methods for continuing research during the pandemic was carrying out surveys; but, for the potential respondents, fatigue arising from receiving multiple surveys from different research groups and adapting to different work environments might have affected the response rate. However, even though there was only one response each from larger biorefineries using pulpwood and their by-products for biofuel and biomaterial production, the survey reached a wide and representative range of small to big heat and CHP plants as well integrated combustion plants with gasification, pyrolysis, and pelletizing (Table 2
), providing sufficient empirical data for a better understanding of the mechanisms of biorefinery and integrated processes that can affect feedstock demand and its preferred properties.
The analysis of expert preferences is a complex task, often carried out using pairwise comparison, which was the approach taken here. Conjoint analysis has been used for choice modeling and discrete choice experiments and is widely used in the social sciences for marketing research and designing new products. The advantage of choice-based methods is that choosing, unlike scaling, is a natural task, of which we all have considerable experience; it is also both observable and verifiable [37
]. The main premise is that the decision maker evaluates the overall desirability of a complex product based on a function of the value of its separate yet conjoined parts [30
]. In this study, the use of attributes and levels to characterize biomass feedstocks and then to rank the main preferences was a simple and clear approach that facilitated a categorization of the heuristics used by the end-users when evaluating feedstock alternatives and making their choices [30
Based on work proposed initially by mathematical psychologists [38
] Green and Rao, [39
] applied the notion of conjoint measurement to discover which product attributes are more important to consumers. The same approach has been used in the forest sector, for example, for the definition of policy instruments [40
], forest contracts [41
], forest conservation programs [42
], initiatives to foster investments in the forest sector [43
], and forest machine manufacturing [44
]. There are alternative methods for addressing similar research questions based on similar data sets. For example, the Analytical Hierarchy Process (AHP) was combined with the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) in a study of the characteristics of biomass for gasification [45
]. However, conjoint analysis has several advantages that justify its use: the overall questions are less demanding because the respondents do not need to produce complex preference assessments and they are not presented with a long list of pairwise comparisons [46
]. Questions are repeated with different pairs of hypothetical alternatives, all involving different combinations of attributes, until enough information about the preferences has been collected to weight the attributes accordingly. In addition, the PAPRIKA method can be described as an ‘adaptive’ conjoint analysis because each time a choice is made it formulates the next question based on the previous choices, facilitating an interaction with the respondent. In contrast to the AHP methods, the number of pairs to be explicitly ranked is minimized by identifying and eliminating all those pairs implicitly ranked as corollaries of the explicitly ranked pairs via the transitive property of additive value models [28
]. This allows more complex sets of attributes and levels to be considered that would otherwise result in exponential numbers of pairwise comparisons [44
]. The responses can then be subjected to mathematical analyses based on linear programming (see [28
]) to calculate ’part-worth utilities’, weighting the relative importance of the attributes and providing a solid methodological basis for further analysis.
Expert-based analyses do not need a large number of responses because they are not based on frequentist methods. A qualified assessment can represent the common practices carried out across a large facility, and our number of respondents is in accordance with similar studies. For example, Kulišić et al. [47
] had 35 and 41 respondents when assessing biofuel policy preferences in Croatia and the BIOEAST region, respectively. Fernandez-Tirado et al. [49
] had 12 respondents when analyzing biodiesel alternatives in Spain, and Schillo et al. [50
] had 33 respondents when analyzing biofuels policies in Canada. Previous studies have also addressed the issue of representivity and the number of responses needed to perform these types of assessments, highlighting expertise as the most important factor to take into account. Even a single expert may suffice as a basis for analysis, and efforts to add additional experts can, in fact, compromise the accuracy of a study if their expertise is not well balanced [51
]. In this sense, the number of experts involved is in line with similar studies and provides a valid basis for analysis, provided the due caution.
The results revealed a wide range in the relative importance placed on biomass assortment attributes, suggesting that each biomass supplier has to look after specific end-user needs, with some concentrating on a single assortment and others considering a larger variety. The broader the accepted assortment is, the greater is the possibility for mixing and matching different biomass sources to deliver an optimal feedstock to the end-user with effects in the procurement and operational costs for logistics operators [52
]. The availability of specific raw material assortments for particular industrial processes depends largely on the geographic location of the facility itself, the predictability of feedstock accessibility, and the surrounding wood-based industrial facilities capable of supplying certain biomass by-products, e.g., bark, sawdust, or shavings [5
], as well as the industrial process applied, such as combustion, gasification, pyrolysis, etc. Depending on the industrial process and the location of the facility, some of the biomass assortments may have to be upgraded to improve their quality and bulk density or/and their supply streams may need to be divided into more precise assortments to optimize the profitability of each biomass unit by delivering the best-suited biomass for a particular industry at the best price [15
]. Thus, not only can extra value be added to the biomass itself, but, under certain conditions, long-distance transportation from biohubs to the industrial plant can be improved with the use of railroads, waterways, or high-payload trucks, reducing traffic intensity and air and noise pollution in populated areas [10
]. Biohubs and terminals are especially important to operators in terms of buffering peak congestion in response to increased logging volumes and mitigating damage as logging moves into increasingly fragile terrains. Terminals can help reduce periods of peak congestion and facilitate the transportation of raw material out of the forest under the best possible weather conditions.
While there are well-established centralized biomass measurement systems in Sweden and Finland, facilities in Australia and Canada are more open to digital measurement and delivery services. Among the countries represented, the Finnish respondents were the most reluctant to move towards electronic billing and measurements outside the receiving facilities, highlighting the importance of the type of biomass feedstock for most decision makers, particularly in Finland and Sweden. This suggests that biomass assortment standards, especially for energy production, are more established in Nordic countries and that decision makers associate many biomass properties directly with a specific assortment. In contrast, biomass suppliers in Australia and Canada can more readily negotiate biomass supply according to specific biomass requirements if they can control its quality.
In recent years, Nordics have seen the development of large forest industry terminals specializing in either industrial roundwood or biomass for energy supplies [6
]. At the same time, Nordic countries have experienced an upscaling of existing forest industry facilities (mainly pulp and paper mills) with the addition of adjacent biorefinery units. This has opened up opportunities to store, modify, and upgrade the quality and bulk density of biomass at one joint biohub or terminal and to deliver several biomass assortments, such as roundwood, logging residues, bark, chips, pre-processed biomass, etc., in bulk [8
]. The different operating environments of biomass suppliers and receivers can provide opportunities for various emerging business models for supplying renewable carbon products alongside a political consensus to reduce or eliminate fossil carbon. Business models indicate how a company can add value to a product, and circular business models can also add value to secondary biomass [59
Another area offering challenges and opportunities is biomass storage and handling, especially in Australia and Canada, where decision makers are more open to sharing their knowledge and handing over some control to suppliers. More than 30% of all facilities reported limited storage capacity followed by a number of other biomass handling-related issues, such as biomass loss as a result of biological activity, self-ignition, and, especially in Australia and Canada, environmental restrictions. If possible, 25% to 75% of the facilities would like to rent out extra storage space to address this problem, but most of them are reluctant to hand full responsibility for the stock over to the supplier.
Biomass handling at suppliers’ terminals, with trusted load measurements, is an interesting area for the development of biohubs, especially in Australia and Canada, where decision makers are much more interested in sharing knowledge and risks with suppliers and are more open to digital payment and measurement services. In combination with smaller combustion and gasification facilities, there is a niche for expert biomass suppliers and smaller, more diversified biohubs. Procurement contract periods are also more diverse in Canada and Australia, where, in addition to shorter-term and mid-term contracts (up to 1 year), decision makers also show a preference for long- and very-long-term supply contracts (of up to 20 years). In contrast, facilities in Sweden and Finland mostly prefer 1-year or up to 3-year contract periods, while facilities during their start-up period and with integrated biorefineries such as gasification and pyrolysis prefer to have longer biomass supply contracts than bigger, well-established facilities. However, because of the relatively low number of responses for each country and technology used, caution must be used when generalizing the results presented here.
Finally, while there was consistent agreement among the respondents regarding many attributes such as low ash, moisture content, and particle size variation, as well as high biomass availability and supply security at a low price, there were a few other factors some respondents took into account. For example, four respondents for mid-sized combustion plants, including one with a pelletizing facility and pellet plant and a small combustion plant in Canada, preferred ash content to be at its maximum acceptable level for their processes, even though it was considered to be the least important attribute. The preferred moisture content level and particle size range also showed a wide range of preferences among facilities, conditioning the options for wood size reduction [60
]. Even among the pellet factories in Sweden and Canada, one might prefer a higher moisture content while another might prefer a medium content, suggesting that some facilities also took in by-products such as bark for their drying processes, etc. Lower grades of biomass can, in fact, be used to help control the main product operations’ processes [61
In the long run, the preferences of end-users will be subject to changes in the overall development of the sector and will have an influence on the associated supply chains. Trends already show greater competition for high-quality, homogenous, and consistent biomass, such as debarked roundwood, sawdust, and shavings, and developments on chipping processes and planning as well as additional sieving of comminuted material could help keep the competitive profile of primary residues [62
]. These sieved, sorted, and, if needed, mixed biomass assortments could be delivered to the right end-user, at the right time and location, via biomass terminals or biohubs. In addition, biorefining processes could build in resilience to biomass heterogeneity and provide opportunities for traditional wood-based industries to make strategic partnerships, move from being secondary biomass suppliers, and transform into a biohub that is able to separate, upgrade, and optimize biomass deliveries at a central node in the supply chain (see [8