Read each of the following passages and answer the items that follow. Your answers to these items should be based on the passages only.
Coal is more abundant, but its solidity makes it less convenient to use. Traditional methods for converting coal to gases and liquids involve complex high-temperature chemical processes. Today’s cheap natural gas has made such techniques unattractive. But coal reserves could last a couple of centuries longer than gas reserves, so scientists are looking for new ways of converting coal into something more useful.
One approach uses fungus. A few years ago, scientists at the University of Hartford in Connecticut found that f2 Polyporus versi-colour f1 turns leonardite, a form of brown coal, into liquid. The fungus was not so obliging with other types of coal. The process seemed to depend on using lignite that contains a lot of oxygen (leonardite is 29% oxygen by weight, compared with 20% for most American brown coals).
The promising results all came from young coals, in which less of the original biology had aged into geology. Perhaps the fungus attacks ether bonds. These contain oxygen atoms, and are found in biological molecules; they tend to break down over time, meaning that older coals-and coals with less oxygen to begin with-have fewer of them.
When bio-technologists think a bond is being broken, they reach for their enzymes. However, the enzyme thought to be responsible for liquefaction, laccase, turns out to be almost useless on its own. So f2 Polyporus-fl and the handful of other fungi and bacteria which have been found to liquefy coal-may be doing something rather more complicated than originally thought.
The fungus’ workings are sluggish, as well as mysterious. It takes its time establishing itself on the coal before producing whatever it needs to begin its attack. Action can sometimes be seen within an hour, but complete liquefaction can take over a week.
The problems have not deterred scientists at Houston Lighting &, Power Company. They envisage large lignite refineries in underground salt caverns. Ground-up lignite would be poured in, together with water and bacteria. With any luck, methane, benzene, organic acids, carbon dioxide and other useful by-products would pour out. Caves and lignite are easily found. It is proving trickier to find a bug that likes a bit of salt, does not breathe oxygen, and reliably excretes methane.
During the process of converting coal into useful liquid form, young coals seemed to be an ideal choice. The reason being that: