The concept of converting human waste into jet fuel might raise some eyebrows, but Firefly CEO James Hygate acknowledges the cringeworthy aspect while also lauding the potential of this resource. Hygate's frank description of the biosolids as "kind of disgusting" but "an amazing resource" underscores the pragmatic approach to utilizing the millions of tonnes of waste that have no intrinsic value.

This device relates to feces and urine elimination cabinets and more particularly to defecation relief devices used by aircraft pilots and other key flying personnel. More particularly it relates to feces and urine elimination cabinets which may find utilization in single pilot driven aircraft.

Comparatively speaking it is an easy matter to provide adequate latrines for the men in the forces on land and sea. When the time comes to eliminate, one just walks to the nearest comfort station. But in the Air Force the problem of elimination can not be always solved that easily especially by aviation pilots...

The applicants are cognizant that there are relief tubes provided on most all jet planes for urinating, but no single seat aircraft is equipped with a safe and sure means for defecation. When the pilot of the jet, due to accident or enemy action needs to eliminate, the problem of defecation becomes acute. The pilot must wait until he lands his craft; and quite often he must remain aloft for a considerable length of time before he has a chance to visit a comfort station on the ground. In many cases due to the physiological and psychological effects produced on the pilot by enemy action, he is forced to eliminate even before he has a chance to land his plane.

Even without water for flushing, toilet wastes are mostly water. Urine is more than 98% water and faeces are more than 70% water. The actual amount of solid matter we excrete is quite small – less than 50kg a year, compared with around half a tonne with all the water included. It is tempting then, and technically possible, to deal with toilet wastes simply by dehydration, and this is the principal method adopted by some commercial dry toilets. One can go even further and incinerate the resultant dry matter, reducing it to a few kilos of ash. One US model, no longer produced, was called the 'Destroilet'...

Disadvantages:

• an electricity connection is needed
• electricity consumption potentially significant – often the toilet will become the largest-consuming appliance in the house
• they are vulnerable to SHOCK LOADS – there is an upper limit to the rate at which it can accept inputs over a short period
• problems often arise if the unit is not in continual use
• the product may be hygienic when removed, but may not be actually composted and requires further treatment to become stable
• there is a risk of total failure in the event of an extended power-cut

Sometimes such compact electrical toilets are the best and only solution, but in practice users are often dissatisfied. The units are very sensitive to misuse – readily overwhelmed by a serious party, for example. Re-commissioning after a breakdown is not a job for the faint-hearted. A common problem arises when the units are installed in holiday-homes and are left for long periods without use. The de-watering process can sometimes transform a mixture of toilet paper, urine and faeces into a kind of paper mâché that coats the innards of the toilet so tenaciously that it is almost impossible to remove. Its strength is so impressive one imagines there could be industrial applications for it.