Oil and gas production handbook An introduction to oil and gas production

Figure 39. Transesterification 
 
Biodiesel contains no petroleum, but it can be blended at any level with 
petroleum diesel to create a biodiesel blend. It can be used in compression-
ignition (diesel) engines with little or no modification. Biodiesel is simple to 
use, biodegradable, non-toxic, and essentially free of sulfur and aromatics. 
 
Although biofuel is carbon-neutral, concern has been raised about diverting 
agricultural areas away from food production. Recently, research has shown 
potential for growing certain strains in arid regions that could not otherwise 
be used for producing human food. 
 
An alternative to the above process that is still at the research stage is 
genetically modified E. coli bacteria. E. coli can produce enzymes to break 
down cellulose to sugar, which can then be used to produce biodiesel. This 
method allows use of general biological waste and limit competition with 
human food resources. 

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9.1.8 Hydrogen 
Although not a hydrocarbon resource, hydrogen can be used in place of or 
as a complement to traditional hydrocarbon-based fuels. As an "energy 
carrier,” hydrogen is clean burning, which means that when hydrogen reacts 
with oxygen, either in a conventional engine or a fuel cell, water vapor is the 
only emission. (Combustion with air at high temperatures will also form 
nitrous oxides). 
 
Hydrogen can be produced either from hydrocarbons (natural gas, ethanol, 
etc.) or by electrolysis. Production from natural gas is often done via syngas 
(see chapter  9.1.5) with up to 75-80% efficiency. Its advantage over 
methane gas is that carbon dioxide can be removed and handled at a central 
location rather than by each consumer, providing a cleaner energy carrier. 
 
Hydrogen is also produced from water by electrolysis with an efficiency of 
about 25% at normal conditions, to about 50% in high temperature, high 
pressure processes, or in various recycling processes in the chemical 
industry. (e.g., hydrochloric acid recycled in the polyurethane process). The 
energy supply can then come from a renewable source such as 
hydroelectric, solar, wind, wave, or tidal, where hydrogen acts as an energy 
carrier  replacing batteries, to form a fully clean, renewable energy source 
supply chain. 
 
In both cases, the main problem is overall economy, distribution and storage. 
Hydrogen cannot easily be compressed to small volumes, and requires quite 
bulky gas tanks for storage. Also, hydrogen produced from electricity 
currently has an end-to-end efficiency that does not compare well with 
gasoline or electrical battery vehicles. 
9.2  Emissions and environmental effects 
The production, distribution and consumption of hydrocarbons as fuel or 
feedstock are globally the largest source of emissions into the environment. 
The total annual world energy supply of 11,000 million TOE is based 81% on 
fossil fuels, and releases some 26,000 million tons of carbon dioxide plus 
other gases, e.g., methane into the atmosphere. 
 
The most serious effect of these emissions is global climate change. The