Advanced bio-hydrocarbons are second generation biofuels and are derived from lignocellulosic biomass such as trees, grasses, waste, agricultural or forest residues, or algae. These fuels are not produced using the agricultural commodities like corn, sugarcane, soybean, etc.
The advance biohydrocarbons does not require significant modification in the existing fuel distribution infrastructure and also the vehicle engine. Advanced biohydrocarbons are also known as drop-in fuel. The energy content of advanced bio-hydrocarbons is equivalent to that of their petroleum-based counterparts. There are several pathways that can produce advanced bio-hydrocarbons. NSF (2008) suggests these primary methods:
- Fermentation (Microbial Processing):The biomass is pre-treated with heat, enzymes, or acids to make the cellulose easier to break down into simple sugars using a chemical reaction called hydrolysis. Genetically engineered microorganism is specially introduced in the sugars from the biomass for the fermentation process quite similar to the process used to ferment corn or sugarcane to produce ethanol. However, instead of breaking the sugars further to alcohol these special micro-organisms break the sugars to hydrocarbons.
- Gasification: In this process, the solid woody biomass at very high temperature is converted to Carbon Monoxide (CO) and Hydrogen (H2), called syngas. Syngas is then further converted to liquid fuel through the Fischer-Tropsch (FT) synthesis. Syngas is the starting material for catalytic chemical reactions for the Fischer-Tropsch synthesis. Hydrocarbon synthesis from biomass-derived syngas (bio-syngas) has been investigated as a potential way to use biomass. Only biomass offers the possibility to produce liquid, carbon neutral, transportation fuels (Tijmensen et al., 2002).
- Pyrolysis: Similar to gasification, the untreated solid woody biomass is heated in high temperature in the absence of oxygen for breaking down the complex lignin structure into intermediate bio-oil. Furthermore, catalytic reaction called hrdrotreating is used to refine the bio-oil produced by pyrolysis.
- Algal conversion: There are currently three main way to produce a fuel from algae: (1) Algae is genetically engineered to secrete bio-oils efficiently; (2) A bio-oil extract from algae is chemically treated to produce a bio-oil; or (3) Algae cultures are converted in their entirety via pyrolysis. The algae can be genetically modified to prosper in otherwise harsh conditions (e.g., high salinity or nonpotable water). In all cases, the bio-oil product derived from algae is refined via hydrotreating and becomes a liquid fuel similar to diesel or gasoline.
Figure 1 illustrates chemical, biological and thermal production pathways for advanced bio-hydrocarbons derived from woody biomass and algae. The production of gasoline, jet fuel and diesel depends on the pathways one follows.
Biological and Chemical Catalysts: All the production processes discussed above are formed as the result of biological and chemical catalysis. Catalysis is a process in which a catalyst is added to a chemical reaction to increase the rate of reaction without being consumed by the reaction. As shown in Figure 1 most of the steps of the biofuel production undergoes with help of chemical reaction.
This algal conversion technology is still in research and development phase and commercially not available. Many studies are been carried out to harvest the algae in large scale. The harvesting technique had been addressed successfully by many industries. Studies show that it will take another 10-15 years for commercial scale production of algal biofuels. For this to be achieved, an economic process must be established that will include efficient algal cultivation, harvesting and extraction (Kovalyova, 2009)
On the other hand, the liquid fuel produced by the FT synthesis has similar characteristics as that of gasoline. The fuel contains neither sulfur nor aromatic compounds which is responsible for soot formation. Commercial airlines in South Africa has been using 50% blend of FT liquids. Plants in Malaysia, Qatar and South Africa (existing and planned) can produce up to 75,000 barrels of jet fuel per day at a cost of $ 1.40 to $2.50 per gallon. (Hileman et al., 2009).
The blue map scenario of Energy Technology Perspective analyses until 2050 shows that biofuels can provide 27% (32 EJ) of the total transportation fuel demand in 2050. As advanced biofuels commercialize, they will eventually provide the major share of biofuel, whereas most oil- and starch-based conventional biofuels are expected to be phased out because of rising and increasingly volatile feedstock prices. The projected use of biofuels could avoid around 2.1 Gt of CO2 emissions per year when produced sustainably (IEA, 2011).
Many developing countries rely on fossil fuel import to meet their domestic energy demands. Developing countries therefore can establish a sustainable biofuel industry to diversify their energy source and decrease their dependency on fossil fuels. This will help improve the economic situation of these countries (UN energy, 2007).
Advanced biohydrocarbons encourages feedstock trade in future for the developing countries. It can also attract the foreign investment, which can help in development of rural sector ultimately leading to enhanced development of feedstock cultivation and handling skills.
In 2009, five major oil companies – BP, Chevron, ExxonMobil, Royal Dutch Shell, and Total announced joint ventures with biofuel companies to work on the development of advanced bio-hydrocarbons. Shell Company in Malaysia has the world’s first commercial-scale gas-to-liquid (GTL) plant based on FT synthesis operating since 1993, and continues to produce approximately 15,000 barrels per day. Estimates of global production of GTL in 2017 are between 200,000 and 300,000 barrels per day (Hileman et al., 2009).
Currently, there are no low-cost technologies to convert the large fraction of energy in biomass or the bio-oils derived from algae into liquid fuels efficiently. There is a need to reduce the production cost for making the bio-hydrocarbon fuels cost competitive (Smith and Allen, 2011). Unless the biofuels becomes cheaper than fossil fuel it cannot compete the fossil fuel market.
Second and third generation biofuel can be successfully developed and deployed only after significant technology improvements. These barriers exist in processes such as selective thermal processing, liquid-phase catalytic processing of sugars and bio-oils, and catalytic conversion of bio-gas (Pew Center, 2010; Sims et al. 2009).
Current support for biofuels generally falls into three categories:1) Policies that mandate levels of use of biofuels, 2) Policies that offer subsidies or tax credits for fuel production and/or use, and 3) Research initiatives.
Policies can play a crucial role in developing the market of biofuels. According to a study by REN21 (2011), almost 31 countries have blending mandates in national level. Similarly, policies that offer fuel-tax exemptions and production subsidies exist in at least 19 countries.
For example, Thailand has blending mandates of B3 and E10, Ethiopia of E10, Brazil of E20-25, India of B10 and E10 as of 2008; B20 and E20 by 2017 etc. Similarly, there is subsidies for public-access biofuel station in USA and fuel tax exemption in countries like Argentina, France, UK , USA, South Africa ( REN 21, 2011).
Socio-economic development: Growing interest in second generation biofuels worldwide is not just due to climate change and energy security but also due to its possible contribution to socio-economic development, outlined below:
- Advanced biohydrocarbons addresses the food security issues as the feedstock for producing these fuels are not the food crops.
- Advanced biohydrocarbons can help protecting the trade balance and foreign exchange of a country. This is achieved by importing less petroleum products.
- Unlike the first generation biofuels, the second generation biofuels create more employment opportunity in the innovative industry which is a highly skilled job and less educated employment in the agricultural sector (Londo et al., 2009).
- The value addition to the residues can increase the rural incomes (IEA, 2010).
- The use of biohydrocarbons has positive health impacts, reducing the level of air pollution and related illnesses (Ewing and Msangi, 2009).
Environmental Benefit / Emission Reduction Potential: The environmental benefits of advanced bio-hydrocarbons are significant. Since climate change is an emerging issue, biofuels have very good potential to address the climate change, land use change and food security issues.
- The primary feedstock for advanced bio-hydrocarbons is woody biomass and algae. These feedstock are unlikely to change the land-use change pattern much and affect the bio-diversity as compared to first generation fuels.
- Advanced bio-hydrocarbon fuels are chemically equivalent to the fuels derived from petroleum, which may make it possible to link bio-refining processes to existing petroleum refineries. This has the potential to reduce the environmental impact of construction of new refineries and distribution networks and other fueling infrastructure.
- Life Cycle analyses of biofuels show that it can replace fossil fuels. Since bio-hydrocarbon fuels have the potential to displace the fossil fuels it has GHG reduction potential as well (Carriquiry et al., 2010). Table 1 compares the GHG mitigation potential of selected biofuels compared to fossil fuels using the LCA technique (Land use changes not included in the analysis).
Currently, second generation biofuels are more capital intensive than the first generation biofuels. It is very important that the biofuel cost is competitive to cost of fossil fuel in order to displace it. IEA (2010) reports that currently the investment cost of second generation biofuel plant with capacity of 50-150Ml/yr. are estimated to be USD 125-250 (IEA, 2008). This is around ten times more than the first generation biofuel. However, in Brazil, China, India and Thailand, large bioenergy projects with investments exceeding USD 200 million have already been successfully completed (IEA, 2010).
There are four primary factors that determine the cost of the biofuels; the feedstock, capital cost (e.g. chemical processing, refining and finishing the crude product), operation and maintenance cost and the transportation and distribution of finished fuel.
- Feedstock Cost: The cost of woody biomass feedstock is dependent on a number of factors including, but not limited to: crop yield, land availability, harvesting, storage and handling, and transportation costs. According to a study by Hamelinck and Faaij (2006) feedstock cost can be up to 45-58% of the total production costs. Hubert (2006) estimates a cost of $34 to $70 per dry ton, or $5 to $15 per barrel of oil energy equivalent. These studies focus mainly on feedstocks like agricultural residue, non-food crops, forest residue, dedicated energy crops and Jatropha and algae. Table 2 shows the estimated cost of selected feedstocks.
- Capital Investment and production cost:Piccolo and Bezzo (2009) presented the capital invested by the processes used to produce the biohydrocarbons fuel; namely enzymatic hydrolysis and fermentation (EHF) process and Gasification and Fermentation (GF) process. The cost is divided into sections for ease. The five sections are a) biomass feedstock pre-treatment, b) Cellulose Hydrolysis, c) Fermentation, d) Separation and e) Effluent treatment. Table 3 gives the detailed breakdown of the overall cost. The plant is assumed to process 700 thousand dry tones of biomass per year.
According to Hamelinck et al. (2005), advanced conversion technologies can reduce the capital investment from $0.95-$1.27 per liter ethanol and reduce the operating cost to $0.11-$0.25 per liter of ethanol.
IEA (2008) have noted that the second generation ethanol production to be around $0.60-1.30/liter range. However, technological advances can reduce the production costs down to as low as $0.30-0.40 per liter by 2020. Though most studies (IEA, 2008; Hamelick et al., 2005; Picolo and Bezzo, 2009) project different cost for biofuel, this is still more expensive than fossil fuels (Smith and Allen, 2011). The most optimistic assumption for cost estimation targets the price of bio-hydrocarbons to come near that of diesel. However, these estimates can vary for large scale productions.
The cost of transporting biomass feedstocks can increase production costs considerably. The savings derived from economies of scale at centralized facilities are often offset by the increased transportation costs of the raw material. Developing a distribution system that is built on local and distributed production facilities rather than large centralized facilities will help reduce transportation costs.
In terms of net production, various start-up companies anticipate that in the long term, advanced bio-hydrocarbons will be competitive with conventional petroleum products at oil prices of about $40–60 per barrel (Regalbuto, 2008).
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