Biorefinery Based on Multiple Raw Materials

Biorefinery Based on Multiple Raw Materials: History

Please note this is an old version of this entry, which may differ significantly from the current revision.

Subjects: Materials Science, Biomaterials

Contributor:

Carmen María Álvez-Medina

In this entry, the possibility of the implementation of a biorefinery based on multiple raw materials (from agricultural wastes, vegetable oils, etc.) is covered, pointing out the available technology to interconnect different processes so that the atom economy of the process is as high as possible, reducing the environmental impact and improving the efficiency of the energy or products obtained. For this purpose, this model is based on previous works published in the literature. The role of biorefineries is becoming more and more important in the current environmental scenario, as there is a global concern about different environmental issues such as climate change due to GHG emissions, among others. In this sense, a biorefinery presents several advantages such as the use of natural raw materials or wastes, with high atom economy values (that is, all the products are valorized and not released to the environment). As a consequence, the concept of a biorefinery perfectly fits with the Sustainable Development Goals, contributing to the sustainable growth of different regions or countries, regardless of their stage of development. The aim of this entry is the proposal of a biorefinery based on multiple raw materials, using different technologies such as transesterification to produce both biodiesel and biolubricants, steam reforming to produce hydrogen from glycerol or biogas, hydrothermal carbonization of sewage sludge to produce hydrochar, etc. As a result, these technologies have potential for the possible implementation of this biorefinery at the industrial scale, with high conversion and efficiency for most processes included in this biorefinery. However, there are some challenges like the requirement of the further technological development of certain processes. In conclusion, the proposed biorefinery offers a wide range of possibilities to enhance the production of energy and materials (hydrogen, biodiesel, biolubricants, different biofuels, hydrochar, etc.) through green technologies, being an alternative for petrol-based refineries.

biomass
biogas
biodiesel
biolubricant
glycerol
transesterification
steam reforming
hydrothermal carbonization
pyrolysis
combustion

1. Introduction

1.1. Current Energy Scenario

In the current global energy scenario, there is an increasing concern about several aspects, such as environmental problems (greenhouse gas emissions, land and water pollution, etc.) or geopolitical issues (such as international conflicts with economic and commercial consequences) that provoke a general worsening of the standard of living of citizens, especially in developing countries. In this sense, the implementation of green policies, including the promotion of a circular economy and green chemistry at the industrial level, could be a very interesting alternative to alleviate these problems [1,2]. Thus, a real contribution to environmental protection could be achieved, as well as a higher energy independence that could neutralize the negative effects of geopolitical conflicts. Finally, these practices could be an important starting point for the sustainable growth of developing countries.

1.2. The Role of Biorefineries

In this context, the role of biorefineries as real alternatives for refineries based on petroleum is becoming more and more important, as their implementation contributes to environmental conservation through green processes and low emissions. Biorefineries can be based on multiple raw materials and technologies to obtain energy and a wide range of products [3,4]. Nonetheless, some points are common in these biorefineries, including:

The starting point of these biorefineries are renewable raw materials or wastes that can be valorized. Otherwise, their environmental management would be difficult, costly, and fruitless. Thus, the avoidance of fossil-based products is a key point to reduce many of the abovementioned environmental and geopolitical problems. For instance, there are biorefineries based on different wastes (such as fruit and vegetable wastes [5], including tropic agro-industrial waste [6], or biomass and waste in general [7]), whose implementation can be interesting.
Considering that the products obtained are derived from natural sources, their environmental impact if there is an accidental release would be less negative compared to petroleum products. It should be taken into account that some of these processes obtain products that partially retain the molecular structure of their precursors, keeping some characteristics (such as high biodegradability).
Different products are obtained, many of them as intermediate compounds that can be reused in further processes depending on the demand. Consequently, biorefineries can be adapted to current energy and product demands. In this sense, when necessary, the production of a certain biorefinery can be centered on goods that are scarce due to geopolitical aspects, as in the case of biofuels when abrupt changes in oil prices occur.
The atom economy (or atom efficiency, defined as the amounts of desired products that are obtained compared to the amounts of reagents used, expressed in terms of percentage) of these processes is usually high, due to the high conversions obtained (with the contribution of catalysts in many cases) and the interconnection with other technologies to reuse intermediate products or wastes. As a consequence, low quantities of pollutants are released to the environment, with a subsequent low environmental impact. In any case, other factors such as the economy or social aspects should be taken into account in this context.
Lastly, many wastes are derived from local or agricultural sources. Consequently, their valorization in a biorefinery context would imply an important contribution to the sustainable growth of developing countries or regions. In these areas, the main agricultural practices can provide products or wastes that could serve as the basis for the implementation of biorefineries specifically adapted to their specific circumstances. However, the real implementation of a biorefinery can be a challenge, requiring environmental and economic analysis to assess its feasibility.

Therefore, different technologies widely studied in the literature for biomass conversion could be interesting, such as pyrolysis or combustion of biomass [8,9], biodiesel or biolubricant production through transesterification [10,11], biogas production through anaerobic digestion with the production of biomethane and the subsequent valorization of CO₂, or biogas reforming [12,13] to produce hydrogen or syngas upgrade to obtain different biofuels through Fischer–Tropsch [14], among many others. These processes and components could be suitable for their inclusion in a biorefinery, as many of the byproducts or wastes obtained in a certain process could be upgraded by using another one, generating synergistic interconnections that result in biorefineries with multiple processes involved.

Indeed, the increasing interest in this field is denoted by the number of registered patents, which could indicate a relevant presence of these processes at the industry level. Thus, Table 1 shows some of the patents related to biorefineries or some of the processes that will be covered in this entry:

Table 1. Patents related to biorefineries or processes included in this entry.

Inventors	Patent	Year	Reference
Shuangquan	Multi-recycling type kitchen waste biorefinery system	2024	[15]
Azocar Ulloa et al.	Microalgae biorefinery for biofuel and valuable products production	2015	[16]
Wu et al.	Method for preparing phenolic compounds by catalyzing pyrolysis of biorefinery residues with attapulgite catalyst	2019	[17]
Prandi	Method for converting a conventional oil, petrochemical or chemical plant into a biorefinery	2017	[18]
Crawford and Schafer	Enhancing a biorefinery with an optional vapor recompression unit while maintaining the ability to operate without the vapor recompression unit	2016	[19]
Rispoli et al.	Method for revamping a conventional mineral oils refinery to a biorefinery	2012	[20]
Bae and Cho	An integrated process for conversion of spent coffee grounds into value-added biochemicals and biofuel	2022	[21]
Feng et al.	Integrated biorefinery process for bagasse	2022	[22]

As observed in this table (where a short selection of patents is included), there are recent patents mainly focused on the implementation of biorefineries or the possible conversion of traditional facilities to green processes. This fact identifies several points, like the following:

There has been a considerable number of patents about the use of biorefineries or green processes and technologies for the last 15 years, proving that this field is becoming a reality nowadays.
There is a wide range of raw materials that are used as the basis of these biorefineries, from microalgae to wastes such as spent coffee grounds.
The role of catalysts in these patents is essential. Indeed, some patents are exclusively focused on this issue.
The conversion of old facilities for biorefinery implementation is also important in these patents, which could be a recurring possibility.

In this sense, both purely scientific works at the laboratory scale and different patents (focused on the industry level) indicate that the role of biorefineries is becoming more and more important in this energy and environmental context.

1.3. Aim and Scope

Considering the above, the aim of this entry was to propose a biorefinery based on multiple raw materials and processes to demonstrate the suitability of multiple green technologies applied to a circular economy. Specifically, this biorefinery would be located in the southwest of Europe, although its location could be different due to the versatility and adaptation to multiple raw materials. In this sense, the city of Badajoz (150,000 city residents) was selected as a location with a great potential due to the nearby presence of a wastewater treatment plant and multiple agricultural areas, which could provide the different wastes or raw materials to feed the whole process. This way, the location was selected to avoid further environmental impacts due to changes in agricultural practices, being adapted to the reality of this region and avoiding the contribution to further environmental problems such as desertification or water stress. Also, the location of this city is interesting, with nearby strategic cities such as Madrid (330 km), Seville (187 km), and Lisbon (188 km). Thus, the shipment of generated products would be feasible, although commercial communications could be improved, as expected with the implementation of railroad lines for high-speed trains between Madrid and Lisbon, among other measures taken by the European Union [23]. For this purpose, different research works of our experienced group, supported by other articles that represent contributions carried out by external researchers, were selected as the basis for this biorefinery, interconnecting different raw materials and their corresponding products or byproducts by using diverse technologies to improve the atom economy of the whole process. Furthermore, the valorization of different wastes that would otherwise be characterized by difficult environmental management was also covered, as in the case of waste cooking oil (WCO). Thus, the novelty of this work consists of showing a feasible example of a biorefinery based on our context, which could also be applied to different scenarios, as many raw materials could be easily adaptable to this biorefinery.

This entry is adapted from the peer-reviewed paper 10.3390/encyclopedia4040090

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