As biobased is often referred to as alternative to fossil based, we could state that it applies to all products can be made from fossil origin but can be replaced by organic resources. This means bio-based would include biochemicals, biomaterials, biofuels and bioenergy. The term “bioeconomy” is not necessarily focused on replacing fossil resources but it is more focused on the origin itself. Therefore it does not only entail bio-based but also food and animal feed (hereafter referred to as “feed”), which have always been of organic origin. This would thus make the bio-based economy a subset of the bioeconomy. Birner (2018) describes the replacement of fossil based resources by bio-based ones as an opportunity inherent in the concept of the bioeconomy. It should be noted however that the distinction between the bioeconomy and the biobased economy is not always clear, and can differ between sources and countries. Sometimes the terms are used interchangeably, for example in Lewandowski (2018).

The biobased economy value chain is integrated with the food and feed production chain through biorefineries that use biomass to deliver biomass components that can be used to make biobased products. Biomass that is used as a feedstock is an organic substance of one of the following types: agricultural crops and residues including lignocellulosic crops and residues (wood, grasses, or non-edible parts of plants) and food crops, fresh biomass (such as grass) and aquatic biomass, such as algae and seaweed (Sharma et al., 2018).

The International Energy Agency (IEA) Bioenergy Task 42 “Biorefining in the Circular Economy” defines biorefinery as the sustainable processing of biomass into a spectrum of marketable biobased products and bioenergy (Lindorfer et al., 2019). In a biorefinery, biomass sources are pre-treated, and then isolation and extraction are performed of valuable biomass components such as carbohydrates, proteins, natural fibers, lignin, specialties and oil and fats that form the basis for further conversion into biobased products (Yue et al., 2014). Various types of conversion can be distinguished: biotechnological and chemical conversion that can be combined with synthesis and modification and polymer processing. Groups of biobased products that can be distinguished are biochemicals, biomaterials, biofuels and bioenergy. Those biobased products can range from high-value, low volume fine chemicals such as pharmaceuticals, cosmetics, food additives to high-volume materials such as biofuels and fibers (Langeveld et al., 2010). A schematic representation of a biomass supply chain for the biobased economy is shown in Figure 1.

Like all mathematical models, biobased logistics models have a goal, or objective function. Often, this is an economic objective, but performance can also be expressed in another sustainability dimension with a social or an environmental objective.

We categorize the scope of the model in four aspects, namely supply chain perspective, decision level, biomass source and biobased application. The supply chain perspective refers to which part of the supply chain is modeled: does the model describe the whole chain, or a part of the chain? Does it have a circular perspective? Decision levels can be divided into strategic, tactical and operational levels. In supply chain management, strategic decisions include network design, facility planning, location planning, capacity decisions; tactical decisions include distribution planning, amount of flow, mode of transportation; and operational decisions include production scheduling, customer demands and pricing (Kumar et al., 2020). The biobased source describes which source is used, and the application describes in which type of application the biobased source is being used after the biorefinery process.

In terms of modelling perspective, we consider three dimensions: the modelling choices (related to probability, time, and objectives), the solution approach (optimization, simulation, a combination thereof, game theory), and whether the modelers have chosen to incorporate modelling approaches from other disciplines. We will further elaborate on the solution approaches and the incorporation of modelling methods from other disciplines in Sections 2.3, 2.4.

Mathematical models can be solved through optimization, simulation or a combination thereof (Bierlaire, 2015). Mathematical optimization models are designed to find the optimal solution given a set of constraints and a goal function. For example, to find the optimal location of a biorefinery to minimize transportation costs given some geographical restrictions. Different methods exist to solve an optimization model, for example, rigorous optimization, fuzzy programming and machine learning.

Simulation models can be used to analyze “what happens if” type of questions, and to compare multiple scenarios with each other. For example, to compare the effect of different fuel demand scenarios on the operations of a biorefinery. Optimization and simulation can also be combined, for example to test the robustness of the solution provided by the optimization (Kleijnen and Gaury, 2003).

In most studies, the inputs are given and the outputs are the main result of the model. Sometimes however, the inputs and output can also be subject to model calculations. In the context of biobased supply chains, we see the following models and computational methods being combined with optimization and simulation models: life cycle assessment (LCA), geo-information systems (GIS) and process simulation. LCA can be used to calculate environmental effects of a production chain. This can be done after the optimization, but it can also be part of the optimization, when the goal is, for example, to minimize environmental impact. GIS can be used to feed the mathematical model with geographical data, and it can be used to depict the suggested outcome on a map. Process simulation is used to estimate the parameters and effects of chemical processes (Chaves et al., 2016).

Figure 2 summarizes the structural dimensions and related analytical categories used in this study.

Table 3 shows the options considered for each of the dimensions of the framework.

In this section, we describe the criteria used to define the search boundaries. This study reviews the literature on logistics and supply chain models for the biobased economy. Therefore, each article that is included in the analysis should be about biobased logistics or the biobased supply chain, and there should be a (quantitative/mathematical) model described in the study. Studies were selected from Scopus and Web of Science, published in English in peer-reviewed journals. Review papers were only used for the introduction of this study but not for the content analysis. Conference papers, book chapters and technical reports were also excluded. As we aimed to focus on supply chain models, studies were not considered for further analysis if their main aim was to generate data, for example, macroeconomic studies, life cycle assessment (LCA) studies and geo-information systems (GIS) models. If those models however were combined with, or used as an input for a supply chain model, they were considered for further analysis.

In our survey of publications, we queried the Thomson Reuters bibliographic database Web of Science and Elsevier’s Scopus database since both are commonly used for bibliometric analysis, but they also differ substantially in coverage (Mongeon and Paul-Hus, 2016). Moreover, we used backward and forward snowballing to extend our literature base with additional relevant papers.

We searched for the combination of specific keywords in the title, abstract, and author’s keywords. The set of keywords used includes:

- “logistic*” OR “supply chain”: to focus the search on supply chain/logistics studies;

The asterisk (*) is used to include different possible endings/spellings of a word, such as modelling, modeling, models.

Two keyword combinations were used:

[(biobased OR bio-based ) AND (logistic* OR (supply AND chain )) AND model*)], and [ (biorefinery AND model* AND (logistic* OR (“supply chain*”))].

The search was done for the past decade; so studies published between 2011 and 2020 were included.

All four co-authors of this study separately scored all studies article based on the title, abstract and keywords in the following manner:

- A high score (1) if and only if:

The paper was only considered for further analysis when the summed score of the (4) authors was equal to or higher than 3. The initial search resulted in a significant paper database (436 studies), which reduced in size after duplication removal and scoring them on relevance (84 studies). Figure 3 shows the initial results as well as how the number of papers was reduced by duplication exclusion and scoring.

The following biomass source types were found in the studies: forest/forest residues, agricultural residues, food waste or side-streams, energy crops, the biological fraction of municipal solid waste (MSW) and biomass of aquatic origin. Figure 4 gives an overview of all biomass sources in a pie chart. Some studies did not specify which biomass source was used, often they just used “biomass” to describe it. In Figure 4, those studies are referred to with “not specified.”’

The biomass sources agricultural residues (35%), forest residues (27%) and energy crops (24%) were most prevalent. The results change over the years: up to 2013, these three were the only sources described in the studies, and from 2014, also municipal solid waste (MSW), food waste, biomass of aquatic origin are mentioned as biomass sources.

As discussed in Section 2, we define the biobased products: chemicals, fertilizer, materials, energy and fuel. However, since there is no universally agreed upon definition, and some studies also consider food and feed as part of the biobased products, we also consider those applications in our studies.

Figure 5 shows that fuel and energy (76%) is the most common application area. The other application areas (chemicals, fertilizers, materials, feed and food) sum up to 24%, and have mainly started to show up in studies published in or after 2018.

In Section 2 we discussed that bioeconomy and biobased are sometimes used interchangeably, and we argued that biobased could be considered an alternative to fossil based while bioeconomy entails everything with of organic origin (applications: biobased and food and feed). Our results showed only three studies that include food and feed applications came up in the search results showing that either most studies also use this definition or that food and feed studies are a longstanding subject of its own and are therefore not marked as biobased.

For each study, we checked if it focused on the whole supply chain, part of the supply chain, and/or if it had a circular perspective. Finally, we checked if collaboration or supply chain integration was discussed.

About two-third studies focused on the whole supply chain (69%) and about one-third (31%) focused on a specific part of the supply chain. Only three studies considered a circular perspective. Of all studies, 13% consider supply chain integration and/or collaboration. This is a low percentage since biorefineries can process streams from multiple actors and for multiple markets (Guo et al., 2020), and logistics collaboration can make it easier to achieve sustainability improvements (Stellingwerf et al., 2018).

We found most papers use a strategic decision level (59%), some approach the problem from a tactical decision level (30%) and a small group chooses an operational decision level (11%). The majority of the studies takes a strategic approach, which links to the majority of the studies taking a whole chain perspective.

Some studies (11) combine decision levels. Alizadeh et al. (2019) are the only authors combining all three decision levels. Most others (8) combine strategic and tactical decision levels, and two studies (Geraili et al., 2016; Gargalo et al., 2017) combine strategic and operational decisions levels.

For the modelling methods classification, we checked which choices were made in terms of probability, time and goal of the model. In terms of probability, we found that 67% of the models uses a deterministic approach, 10% use a stochastic approach, and 23% combines both approaches. In terms of time, 25% uses a single-period model and 75% uses a multi-period model. In terms of objective function, 70% uses a single objective, and 30% uses a multi-objective approach. Section 4.6 describes specifically which objective functions were used.

Thus, in terms of probability, deterministic models are most common, in terms of time, a multi-period approach is most common, and in terms of goal, the single objective is most often used. The multi-period aspects of the models can be linked to the seasonal nature of biobased supply chains. Despite the fact that deterministic models are most common within this selection of studies, there is an increase of the number of stochastic models over the decade.

The solution approaches found can be grouped into optimization, simulation, a combination of optimization and simulation, and game theory. Next to that, part of the studies use combined methods in which either heuristics or simulation or both are combined with GIS, LCA, or process simulation. Note that, in terms of solution methods, with simulation, we mean event-driven simulation. While in the combined methods, we check for process simulation which is a method used in chemical engineering to help with analysis, design and optimization of chemical processes (Chaves et al., 2016). Figure 6 depicts the division of those methods among the studies.

Figure 6 shows that optimization is most frequently used (75%, 64 studies), followed by a combination of optimization and simulation (18%); simulation is used in 6% of the cases, and 1% of the studies (1 study) used game theory.

Of the studies that used optimization, most used rigorous optimization; 8 used heuristics techniques to get to a solution within an acceptable computation time, 3 used fuzzy programming, and 1 used machine learning. Note that half of the studies using heuristics appeared in 2019 and 2020, so that seems a recent development.

Of the 84 studies that used optimization, simulation, or a combination of both, 33 studies combined this with LCA, GIS or process simulation. Table 5 shows which combinations of solution methods and computational models were used.

GIS was used in 17 studies, LCA in 11 studies, and process simulation in seven studies.

The objective functions found can be grouped into economic, environmental and social objectives, and into a combination of those. Figure 8 shows the division of the different objective functions over the studied papers.

Figure 6 shows that most studies focus on a single economic objective (72%). This is an interesting observation since almost all of the studies give environment-related reasons as a justification for executing their study. 16% of the studies combined economic and environmental objectives and 11% had objectives in the areas of all three sustainability pillars: people, planet and profit, for example, Chávez et al. (2017). Over time, there is no clear trend in terms of objective functions.

For all studies we checked if they had a case study, and if the authors described where the case study was executed or on which geographical region the data were based. Most studies (63 out of the 84) described the case study location, the others did not describe their location, did not have a case study, or their case study was based on a hypothetical example. Figure 7 shows the division of case studies according to continents.

Figure 8 shows that most studies (62%) were performed in North America, followed by Europe (15%), South America (11%), Asia (10%) and Africa (2%). The case studies are not evenly distributed geographically. This is striking since the biobased economy is something that is relevant to the whole world.

Since most studies were performed in North America, we checked if there were differences between the studies that were performed there, and the studies that were performed in the rest of the world. We took the rest of the world together since we only have a few of those in our database, so if we grouped them per continent, we would not be able to make statements about them. The results are shown in Table 6.

Most categories do not show much differences between North America and the rest of the world. However, the following areas show interesting differences. Studies in North America focus less on using agricultural residues compared to the rest of the world, and less often specify the type of biomass used. Also, all studies using biomass of aquatic origin were performed outside of North America.

Outside of North America, collaboration or integration was studied relatively more often. In terms of solution approach, it is striking that optimization was used in all of the studies outside of North America (sometimes combined with simulation), and in North America, simulation was applied more often. In terms of combination with other computational methods, GIS is applied a lot more often in North America, while LCA is more common in the rest of the world. Both North America and the rest of the world focus on economic objectives, but studies performed in the rest of the world more often also used environmental and social objectives.

In this study, we have collected, selected, and analyzed studies in the last decade on logistics and supply chain models for the biobased economy. We have found that most models are optimization models aimed at minimizing economic impact. Some more recent studies also combine the optimization methods with other methods such as LCA, GIS and process simulation–primarily used to obtain input data for the optimization model. In the studied literature, the main biomass sources are forest (residues) and agricultural residues. The main biobased product applications described are fuel and energy. However, both feedstock and application areas are diversifying. Since 2015 we have seen an increase in type of sources and applications in the publications that we studied.

Over three quarter of the case studies where the location was described, was executed in or based on data from North America; we do not think this is a good representation of the amount of biobased initiatives and research over the world. We also found that studies focus mainly on the strategic decision level and mostly cover the whole supply chain, or at least the supply chain up to the biorefinery. Finally, most of the times models are used to make supply chain design decisions. The fact that biobased logistics models often take a strategic perspective is possibly because biobased supply chains are relatively new, and therefore, a majority of studies will focus on design-related problems.

The abovementioned findings are in line with the results reported in other studies. Acuna et al. (2019) describe that existing biomass logistics and supply chain model studies mainly focus on economic optimization, and Ghaderi et al. (2016) state that most of those models focus on single-feedstock supply chains. Malladi and Sowlati (2018) discuss that most biobased logistics models are about supply chain design of biofuel and bioenergy production, and that recently, supply chain models that focus on other types of biobased products have started to develop.

One of the limitations of the methodology used is that studies that are relevant but do not use the exact wording that we searched for, will not have appeared in the results. Also our scoring method is not completely objective. However, we have aimed to make our literature search as clear and reproducible as possible.

Many studies mention sustainability as a reason to focus on biobased rather than fossil resources. However, the majority of the models in the studies discussed only have an economic objective. Some studies combine economic and environmental objectives, and even fewer studies also consider a social objective. A recent literature review of biorefinery supply chain design (Pérez et al., 2017) confirm this observation: they show that very few investigations have considered all sustainability dimensions when designing the strategic planning of biorefineries in a territory. The focus on the economic aspects can be explained by the low-profit margin in the biobased sector. Additionally, some of the presented works aim at performing a feasibility study for a specific source or region, and accordingly, economic viability has been a primary concern. Despite this fact, in our opinion, future research should include all three sustainability pillars. Therefore, there is a need for more modelling efforts that look at economic, environmental and social objectives in a holistic way.

In operations research, especially sustainability-focused studies, often a trade-off between multiple objectives is calculated. However, in the studies analyzed for this review, only few authors incorporated such a trade-off curve. Therefore, this is a possible future research direction as well, which was also pointed out by Malladi and Sowlati (2018). In terms of methodology, this will imply using, for example, Multi-Attribute Decision Making models, Multi-Criteria Decision Making models and the epsilon-constraint method (Mavrotas, 2009; Huang et al., 2011).

Almost all studies are about real case studies. Generally, they combine model and a specific biomass source and a biobased product application. However, over the studied decade, there has been an increase in using the more general term “biomass.” So both source and application remain unspecified. The complexity of the supply chain models has also increased. At the beginning of the decade, most studies applied operations research methods to a case study and more recently, the complexity of biobased logistics (with uncertain and seasonal supply, and multiple inputs leading to multiple outputs) has given rise to supply chain models that are not focused on solving a real life problem but on solving an abstract version of a problem. The added complexity is also a reason for the recent increase in the use of heuristics and different types of mathematical approaches. Other studies confirm these observations: Ko et al. (2018) describe that biomass supply chains are more complex than standard fossil-based supply chains due to their specific challenges. Atashbar et al. (2016) mention that there is a need for further integration and optimization of the whole supply chain, taking into account more complexity. This current study shows that biobased logistics models are starting to develop into that area.

This study showed an increase in biomass sources and products. In the definition we used, feed and food are not part of the biobased products. However, several studies considered feed as a biobased outlet, and there was even one study that also considered food as biobased outlet. With the introduction of a further collaboration between food and biobased sectors, supply chains will become more integrated and the distinction between the biobased economy and the bioeconomy will become less clear. Guo et al. (2020) do consider food, feed, and biobased together and show that these chains can be complementary.

Most of the studies we analyzed base their findings on case studies in North America. Other parts of the world are underrepresented in this topic, while geographical differences influence whole biobased supply chain. Therefore, we encourage scholars to pick a case study outside of North America.

Of the studied papers, 13% consider supply chain collaboration or integration. An integrated approach can help to deal with uncertainty in supply because of, for example, fluctuating yields. In the case of a biorefinery, integrating supply chains can help to benefit from economies of scale. The integration would also imply involving multiple actors (or their interests) in the decisions process. A modelling approach to tackle this is (cooperative) game theory. Only a couple of articles used such a multi-actors methodology for analyzing decisions in a biobased supply chain [i.e., (Jonkman et al., 2019) and Golecha and Gan (2016)]. However, most other studies assume there is only one actor (or problem owner) or one objective function for all supply chain actors. Considering multi-actor characteristics of biobased supply chains is an important direction for future research. In terms of methods, game theory and agent-based modelling are potentially useful to tackle the challenges in integration and collaboration in biobased chains. Torres et al. (2015) divide use a multi-actor approach by dividing a biorefinery optimization problem in two subproblems: the supply and the demand of intermediates. The actors on both sides of the problem can optimize their part separately while their solutions are coordinated to ensure a feasible biorefinery complex. In their follow-up study, they propose and develop a game theoretical framework and specific methodologies, which allow the optimal design of distributed processing systems, through the decentralized strategies of independent actors (Torres and Stephanopoulos, 2016). Their approach, combining chemical engineering, mathematical optimization and game theory, is very promising. However, only one of the citing studies uses game theory (Chang et al., 2018) but not in a biorefinery context. Thus, there is still enough room for researchers to cooperate and explore this research direction.

Since supply chains are becoming more interconnected and interdependent, supply chain disruptions can become a risk. To deal with this, supply chain resilience has been studied in different contexts, for example, the chemical supply chains (Behdani et al., 2019) and food supply chains (Bottani et al., 2019). One study in our review database incorporates resilience (Maheshwari et al., 2017). They study resiliency optimization of the biomass to biofuel supply chain. To deal with future challenges, more studies on the biobased economy should consider incorporating resilience in their supply chain models.

In many studies, waste streams are considered as a source of biomass. However, only two studies in our literature database considered circularity or had a circular perspective. Our study has shown that the biobased economy does not only include relatively lower value biofuel and bioenergy products, but also higher value biobased products such as biochemicals and biomaterials that can potentially be re-used. Therefore, the scope of biobased logistics supply chain models should extend to also consider use (so also include the demand side) and re-use and take a circular perspective. This will further increase the complexity of the models because of fluctuation in supply, in expected yield and in composition. Moreover, these re-use streams are often difficult to preserve (De buck et al., 2020). The study of Yeo et al. (2020) is an example of how we expect more future research to consider circularity and complexity in biobased logistics is. They model circular supply chain design for palm oil by, for example, reusing the waste streams for produce electricity. In their supply chain model, they integrate the process design of biorefineries. Also, graph theory is used to test the supply chains.

In this study, we grouped a study into “studies the whole supply chain” it started with the biobased source (e.g., tree trunks) and considered the supply chain up to the market. However, biomass is generally grown on land and the market involves consumers that use a product and dispose of it (depending on the nature of the product). Considering circularity in supply chains is more than considering re-use of water in a biorefinery, it involves a cradle-to-cradle approach where the use and re-use is considered in the design phase (Muscat et al., 2021). It requires a holistic perspective and collaboration with people from other disciplines.

Because of externalities like carbon emissions, we expect policies to stimulate the use of biobased products and to reduce, and in time phase out, the use of fossil products. Both fossil and biobased products fulfil a demand for carbon. When that demand cannot be fulfilled from fossil resources anymore, it needs to be fulfilled by recycling, by using biomass and by converting CO₂ into useful products using Carbon Capture and Utilization (CCU) technologies (Muscat et al., 2021). CCU technologies can be combined with bioconversions, as they often emit or consume carbon dioxide. These technologies are under development and to support these developments, smart supply chain decisions should be made. This is a promising topic for future research.

Next to enabling circularity, another reason to consider the demand side is that will help choosing to produce in-demand, higher value products. This will become more relevant when moving from fuel and energy production to different products. To predict demand, studies could use macro-economic models to predict which products will be in demand and adjust the processes in the biorefinery accordingly.

The food supply chain is an example of a chain that is more demand-oriented, and research in food supply chain management has focused on valorization and diversification of the different (side) streams in the production process. Also, there is a vast amount of literature focusing on food quality management in the supply chain, for example (Tromp et al., 2016; Stellingwerf et al., 2021). As biomass supplied in biobased logistics can be subject to decay, models considering food quality in logistics could be used as in inspiration to develop models that help optimize the supply and product quality in the biobased supply chain.

Biobased supply chains (and models describing them) are increasingly becoming multi-feedstock, and multi-application, which means that there are an increasing number of variables to consider when making an optimal decision. Next to this increased complexity, multiple objectives should be considered to be able to meet sustainability requirements, and those objectives can be conflicting. This will make decisions and models to support those decisions increasingly complex. To deal with that complexity, future research should continue to incorporate methods that help reduce calculation time.

To make logistics and supply chain models contribute to a sustainable biobased economy, researchers should aim to incorporate people, planet and profit objectives and circular perspectives into their studies. This will cause increased complexity, which requires new methodologies and collaboration from researchers from different fields and backgrounds. Our study shows the complexity of biobased logistics: knowledge from different fields such as chemical processes in bioreactors, sustainability analysis, operations research and mathematical modelling, needs to be combined to address challenges in these fields. This way, these biobased logistics supply chain models can contribute to tackling the challenges that the biobased economy has to offer.