Energy Sources vs. Construction Materials
One of the hot controversies in the United States is the effect of carbon dioxide on climate change. It ranges with such vigor that some basic chemistry is neglected. It is common for many to consider that all of the components of all types of crude oil would eventually be turned into carbon dioxide, but that is not true. Very light crude oils will contain components which will mainly be used to produce energy, however what are called heavy crudes contain asphalt, which is a construction material not a fuel. Virtually all of the carbon in asphalt is placed on the ground as roads, on roofs, on reservoirs or for other uses that benefit mankind. (One might say that tar and feathering is not constructive, but that depends on to whom it is done). Even after asphalt grows old, it can be recycled. Indeed, there are data that suggests that pavements, when recycled properly, will not age as fast as pavement using new asphalt.
The amount of asphalt in crude oil varies from none such as with Katapa crude from Indonesia to as much as 65% for some California Costal crudes. It is interesting that certain forces demand that the Keystone XL pipeline be stopped, which would ship heavy crude (high asphalt content) but are silent when we import light crude (low to zero asphalt). The amount of carbon dioxide released into the air from the use of the products made from a barrel of imported light crude oil would considerably exceed that released from the products made from a barrel of a heavy crude brought in from Canada.
Biofuels. It is quite reasonable to replace petroleum based fuels with biofuels if a reduction in net carbon dioxide production occurs. (Unfortunately in some cases exuberances trumps chemistry. In my case, the addition of 10% ethanol in our gasoline reduces the mileage of my car by 10%.) It is quite reasonable to turn spent cooking oils into a fuel for diesel engines, and such products are on the market. Eventually other biomasses will be converted into fuels or chemical feed stocks.
Bioasphalts. I would like to suggest that developing Bioasphalts may be more complicated. First, it important to understand what happens in a refinery. All of the products in crude oil are separated simultaneously. Gasoline, kerosene, diesel (#2 fuel oil), light lubrication oil, and a heavy “lube stock” are all distilled off at the same time. Asphalt, if present, remains on the bottom (non-distilled). A refinery tries to select a slate of crude oils that allows a balance among the product since all products come off at the same time. Each distilled product must be removed timely by pumps in which case any pump that reaches its capacity will determine the capacity of that refinery even if that is below the rated capacity. Also, if the refinery can’t sell or store all of the products it makes, it must shut down when the storage tanks for any one product is at capacity. One use of the bottoms is as a heavy fuel, but that would be the case mainly if there is no other more profitable use at the time for asphalt. Other uses of the asphalt portion from a crude is to make coke for steel production or “cracking” the asphalt to extinction in order to turn it into lighter combustible products.
Asphalt by its nature continues as “sequestered” carbon. If Bioasphalts were arbitrarily required to replace asphalt, or specified when there is an excess of asphalt, the bottoms created in refining will have to be coked or cracked, “un-sequestering” the carbon, or the refinery will have to shut down. This can be a problem in the northern part of the country. Often Customers of the refinery may put in large asphalt storage facilities that they fill during the winter with cheaper asphalt.
On the other hand, if there is a shortage of asphalt, Bioasphalts provide the opportunity to essentially sequester bio-produced carbon rather than allowing it to be made into fuel or to decay naturally which would result in the carbon returning to the air.