Green Diesel: An Alternative to Biodiesel and Petrodiesel

First, second, and third-generation green diesel are being considered as promising alternatives to petrodiesel in terms of renewable energy demand, process economic, and environmental concerns. Green diesel is an advanced biofuel that can be produced from different cellulosic biomass such as crop residue, forestry waste or woody biomass. As green diesel has identical chemical properties to petrodiesel, it could be used in its pure form or blended with petrodiesel. This chapter covers the literature related to the different feedstocks (First, second, and third-generation) used for green diesel production, hydroprocessing technology, catalytic materials for such processes, characterization of green diesel, comparison between petro-diesel and green diesel in terms of physicochemical properties, techno-economic analysis, and life cycle assessment. Besides, this chapter covered the current status of the green diesel industry from various commercial plants such as Neste, Honeywell, and ExxonMobil. This chapter discusses several commercial plants that are proposed, under construction or expansion stage, for the production of green diesel.

Green diesel is an alternative fuel generated by the hydrotreating of oil or fat. Green diesel is a kind of next-generation diesel that can be derived from renewable feedstocks. A large range of feedstock is available for the production of green diesel. Various generations of feedstock such as 1st generation (Edible oil—sunflower, palm, corn, rapeseed, and soybean), 2nd generation (Non-edible oil—Jatropha and castor bean, plant waste biomass, and animal fat), 3rd generation (Microalgae) are being used for green diesel production. The chapter sheds light on the different feedstocks used in the production of green diesel along with their chemistry and classification. The use of different feedstock imparts distinct impacts on the production of green diesel. These impacts result in different fuel properties thereby leading to different effects on internal combustion engines. The type of production technology depends on the feedstock used. This chapter also discusses sources, distribution, properties, typical composition, comparative advantages and disadvantages, and current scenarios on commercial feasibility of each generation of feedstock. This is an insight for utilization of feedstocks for green diesel production along with generations.

This chapter reviews green diesel alternately known as renewable diesel production pathways through deoxygenation routes with catalytic interventions. Deoxygenation processes of green diesel production involve milder reaction conditions than conventional biodiesel production thus appear more promising with respect to environmental and economic sustainability. The activity and selectivity of catalyst material depends on several factors among which reaction conditions (pressure, temperature, duration), type of catalysts, support (organic or inorganic or combined), and promoters are of maximum significance. In recent years, high activity and selectivity are being accomplished via deoxygenation with non-noble metal catalysts. Overall, present advancement/progress and forthcoming developments in green diesel production are thoroughly articulated in this chapter.

Non-edible vegetable oils can be converted into diesel fuel by esterification (biodiesel) or hydroprocessing. Biodiesel contains oxygen atoms, whereas hydroprocessed vegetable oil, also known as green diesel or paraffinic diesel, is a pure hydrocarbon (drop-in fuel) with no oxygen atoms. Non-edible vegetable oil such as Jatropha curcus oil can be converted into a hydrocarbon mixture by hydroprocessing. The technology involves pre-treatment of plant oil followed by hydrodeoxygenation, hydrocracking, hydroisomerization, and aromatization. Hydrogenation is employed to saturate the double bonds and remove the oxygen from the triglyceride’s fatty acid chains, either water or CO₂. Subsequently, the other reactions occurring during the process are hydrodesulfurization, hydrodenitrogenation, decarboxylation, and decarbonylation. The feed is processed over the catalyst under hydroprocessing conditions to convert the renewable source into n-paraffins and iso-paraffins. The selectivity of the produced n-paraffins and iso-paraffins range may be shifted to ATF and diesel by suitably selecting the active metals, support, and process conditions. Non-precious metals are used as active metals in the catalyst. The metal oxide or mixture of metal oxide, zeolite, and/or a combination thereof is used as support. Non-precious metals including nickel (Ni), cobalt (Co), molybdenum (Mo), tungsten (W), or a combination thereof, e.g., nickel-molybdenum (NiMo), cobalt-molybdenum (CoMo) and nickel-tungsten (NiW), are used as active metals. These active metals are supported in mesoporous ϒ-alumina (ϒ-Al₂O₃), silica-alumina, and/or zeolite, or a combination of thereof. The active metal(s) are generally in sulfided form. The renewable source is the oil originating from vegetable and animal fats. It includes, but is not limited to, waste restaurant oil, soyabean oil, jatropha oil, algae oil, etc. These oils mainly contain free fatty acids and triglycerides. Different commercial plants for the production of green diesel have been installed worldwide. Renewable Energy Group Inc., Neste, Eni, Total, BP, Cetane Energy, Eni/Honeywell-UOP, and Haldor Topsoe are the key players who developed the green diesel process and produce green diesel commercially. Indian Institute of Petroleum in India had made green diesel from non-edible waste oil via hydroprocessing technology and tested it on diesel engines and diesel generators. The COx, NOx, and particulates emission was reduced significantly while using green diesel.

The decimation of fossil fuel and rises in environmental issues are induced by the increasing global consumption of fossil fuel. This phenomenon is forecasted to increase gradually and has caught serious attention from researchers and governments around the world to discover and develop a cleaner and greener fuel-like biofuel. Green diesel has been crowned as the best biofuel to successor fossil-based diesel owing to abundant feedstocks, eco-friendly process, and lower technology price. Green diesel is produced using heterogeneous vegetable oils and catalysts under hydrogenation process, supercritical reaction, alkali catalyzed process, deoxygenation technology, and hydroprocessing (HP) technology. Nonetheless, the HP technology is enthroned as the most popular technology in producing green diesel in which its process can be maximally enhanced by optimizing operating parameters, harnessing the proper oil, improving and modifying the catalysts and utilizing micro- and nano-sized catalysts. This chapter focuses on the improvement of the catalyst capability and increases the HP technology performance. The improvement of the catalysts has positively contributed to the strengthening of Bronsted-Lewis acidity and enlarged catalyst active sites leading to escalate the HP efficiency, conversion (~100%), selectivity (95%), yield (97%), and reusability (~5 cycles), and further producing less oxygen-contained green diesel.

All over the world, an increase in biofuels consumption, e.g. green diesel, reduces the cost impact and dependence on petroleum and detrimental environmental consequences. Green diesel, next-generation fuel, an alternative energy product, has a similar molecular structure as petroleum diesel but provides better diesel properties. It has exceptional storage stability and is completely compatible for blending with the standard mix of petroleum-derived diesel fuels. The green diesel has been produced by hydrotreating triglycerides or vegetable oils with hydrogen. It is produced using the same feedstocks as biodiesel (mainly animal fats or vegetable oil) but the production process for both differs significantly. It is an optimum biocomponent for blending into mineral diesel. The high quality of green diesel is determined by its higher heating value and energy density, high cetane number and outstanding cold flow properties. Also, the low density of green diesel makes it a very good blending component for refiners, which are usually limited in accepting heavy gas oil bases in the diesel blend. In addition, the low aromatic content benefits from blending with other petroleum diesel bases. The various oxygenates produced that may be considered as additives for diesel fuel are various alcohols, ethers, esters, acetals and carbonates. These fuel additives also lead to the production of specific products that meet international and regional standards allowing the fuels trade to take place. The future production of these additives needs the development of the integrated production process or reactive separation technologies, which helps in the reduction of energy consumption and capital costs. The production of these green diesel additives provides clean and efficient technology. The technical and cost analysis of these production technologies depends upon the unit plant capacity and feedstock price. Unit capacities of the investigated processes that are below 100,000 tonnes/year are likely to result in negative net present values after 10 years of the project lifetime.

Diesel-range hydrocarbons derived from biomass have similar chemical compositions and physicochemical properties with petroleum-derived diesel, known as green diesel. Green diesel also meets the American Society for Testing and Materials (ASTM) specification ASTM D975. Green diesel is thus compatible with existing petroleum pipelines, storage tanks, fueling stations, and diesel engines. Currently, green diesel is produced from non-edible tree-borne oils and lignocellulose biomass. Hydroprocessing of oils and fats, biomass-to-liquid, and a combination of fast pyrolysis and hydrodeoxygenation of bio-oil, are some of the thermochemical processes used to produce green diesel. While commercial technologies are available for producing green diesel from oils and fats, these technologies are suffering from the challenges of the dearth and high cost of feedstock. On the contrary, lignocellulosic biomass is abundant and inexpensive. However, the technologies for converting lignocellulosic biomass to green diesel are in the developing stage. This chapter presents the existing and upcoming hydropyrolysis technologies for converting lignocellulosic biomass to green diesel.

Green diesel is a second-generation biofuel exhibiting comparable physicochemical structure as petroleum diesel but better diesel properties and is considered as an alternative energy product. It is produced from the hydro-processing of fatty acids in a temperature–pressure range of 600–700 °F and 400–100 atm pressure. Green diesel is made of linear and branched pure paraffin in different proportions, and due to its chemical composition and significant variation in the degree of isomerization occurs, it is considered an effective biocomponent for blending into mineral diesel. However, the emissions from diesel causing sustainability issues and contribute towards severe health and environmental impact. Therefore, the appropriate fuel properties and their characterization are essential to maintain the quality of green diesel and to meet the desired requirements at affordable, feasible, and variable process cost, thus facilitating the integration with existing petroleum refineries. The quality of green diesel is determined by its high heating value, energy density, cold flow properties, and high cetane number. The low density and aromatic content of green diesel are the promising features that make it a good blending material as other petroleum diesel blends in the refineries. Quantification and analysis of organic and elemental carbon fractions are performed by a thermal-optical transmission analysis method, acid value of the green diesel is measured by AOCS method, other fuel properties including viscosity, iodine value, flash point, and copper strip corrosion are measured by the ASTM D6751 and EN 14,214 standard protocols. The properties of vegetable oil-derived green diesel such as loading facilities, storage, and logistics are similar to fossil diesel but have a very high cetane number. Application standards of green diesel in CI engine with respect to efficiency parameters, emission patterns as per EURO norms, etc. are some additional aspects that have been addressed.

In the post-COVID-19 era, sustainability is a crucial aspect that includes natural resource management, environmental impact reduction, and socioeconomic issues. Due to the depletion of world petroleum reserves and the greenhouse gas emissions connected with their usage, it has become more evident that continuing reliance on fossil fuel energy resources is unsustainable. As a result, there are active research efforts underway to produce alternative renewable and carbon–neutral biofuels as alternative energy sources. Because of the easy access to feedstock, decreased emissions, and unusually high cetane number, green diesel is becoming increasingly popular in academics and research. This chapter focuses on the background of biodiesel and green diesel fuels and the current status of the industry, and provides insight into the future of green diesel in the world. This chapter mainly deals with biodiesel/green diesel production routes, catalysts employed for the production of green diesel, factors affecting the green diesel production process, fuel properties of different diesel fuels. It further addresses the potential production of biodiesel/green diesel in the world and examines the status and contribution of diesel fuels derived from vegetable oils and animal fats. It was observed that biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demands.

This chapter emphasized a comparison between biodiesel, green diesel and petrol diesel. In general, diesel is referred to any liquid fuel specifically designed for the automotive engine as a fuel. Generally, biodiesel is an alternative fuel that has similar properties to conventional diesel fuel. Biodiesel can be produced from vegetable oils, animal fats or waste cooking oil via catalysed transesterification process. Biodiesel is renewable energy, nontoxic and biodegradable and may reduce net carbon monoxide emission by 78% compared to petrol diesel. Green diesel is one of the alternative fuels which has a similar molecule structure as petrol diesel and yet it provides better diesel properties in terms of higher heating value, energy density, very high cetane numbers and outstanding cold flow properties compared to conventional biodiesel. Green diesel is produced by hydrotreating triglycerides in vegetable oils with hydrogen. The most common type of diesel fuel is petrol diesel. It is produced from the fractional distillation of crude petroleum between the temperature of 200 and 350 °C at atmospheric pressure resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule.

Climate change represents a major challenge for our world’s equilibrium and society. Therefore, we need to implement an adaptive energy matrix where fuels like fossil diesel are used wisely in coming years, but where sustainable and renewable biofuels increase its contribution to the transport sector or in electric power generation. Among those renewable biofuels, biodiesel and green diesel may play significant roles through circular economy of biomass, with local and regional production into a biorefinery with minima emissions and waste streams. The assessment of a particular scientific development may be approached by the techno-economic analysis (TEA) of the production process, which may serve to identify scientific and technological limitations and challenges that impact economic and financial parameters. In this work, we present and discuss the advantages and challenges of blending biodiesel or green diesel with fossil diesel, the technological, economic and financial issues that must be approached by TEA and its constrains, and the comparison and discussion of several TEA works dealing with biodiesel and green diesel production. Even if green diesel is just recently available with respect to biodiesel, it represents an important opportunity in co-processing plant oils into a petroleum refinery, access to high volume capacity plants and distribution, which may help to decarbonize the petroleum fuel sector.

Renewable diesel or green diesel is a positive approach to overcome the related issues associated with other biofuel formulation techniques such as gum formation (biodiesel), poor fuel properties, and the issue of phase separation (pyrolysis oil, other advanced biofuel, etc.) and the long-term operation effects. Green diesel is a straight chain paraffinic hydrocarbon which is free of aromatics, oxygen, and sulfur, and also contains high cetane number. In this experimental investigation, formulation and application of Mesua Ferrea L. vegetable oil-based green diesel have been discussed. Comparative assessment of green diesel and petrodiesel had depicted that the performance, combustion, and emission of CI engine were superior to green diesel. Improved fuel properties of green diesel enhanced the combustion characteristics of CI engine which reflects its superiority w.r.t petrodiesel. The effects of green diesel were also measured at a low CI engine compression ratio (15:1), to measure its better suitability.

The future road transport fleet is expected to involve the need for a mix of fuels (hydrogen, electricity, liquid biofuels, etc.). Among the biofuel alternatives, green diesel–also known as hydrotreated vegetable oil (HVO)–could play a significant role within prospective fuel production mixes. This chapter presents an energy systems optimisation model for an exploratory scenario on the deployment of green diesel in Spain, involving technology characterisation, carbon footprint behaviour, and long-term envisioning. The results show that HVO based on second-generation biomass would lead the deployment of green diesel as an alternative fuel, requiring the installation and use of new production plants to fulfil the ambitious demand expected for the road transport sector. Despite such a potentially high demand, the associated carbon footprint would remain low over the considered time frame. In fact, the total carbon footprint associated with second-generation biofuels would be below 5 Mt CO₂ eq in 2050. It is concluded that future decisions on the decarbonisation of the transport sector could promote the deployment of cost-effective technologies for the processing of second-generation biomass, including the production of advanced HVO.

Green diesel, also known as paraffinic diesel, is a promising next-generation automotive fuel produced from non-edible or waste vegetable oil through alkali catalyzed transesterification, hydrogenation, and supercritical non-catalytic transesterification. The sustainability of green diesel technology relies on robust policy and acceptance among the stakeholders. Further, the economics of green diesel production technologies are strongly affected by the feedstock cost, hydrogen requirement, and the production capacity of green diesel and its by-product yields. Selecting an appropriate manufacturing location would be promising in decreasing the production cost and improving green diesel economics. Integrating a green diesel plant with a petroleum refinery would enable the utilization of process water, hydrogen, heat (for making steam), and other utilities. Further, the production capacity of the green diesel plant must be at least 0.1 million tons/year to avoid negative net return (or annual profit after the tax) and a more extended payback period. Moreover, the sustainability of vegetable waste-to-green diesel technology also needs the policymakers’ fruitful decision on subsidy and tax exemption for green diesel. With the new specification of paraffinic diesel (EN 15940) by European countries, researchers and industries around the globe are looking for the best technological options for a suitable choice for its commercial production.