Turning Waste Olive Stones Into Bioethanol

I wonder if there would be a net benefit from using the 'stones' like wood pellets and burning them in a boiler directly...

As per defination of Olive stone, it is an excellent source of raw materials for ethanol production and lignin as by-product. Olive stone has some advantage on collection, storage point of view compared to other agricultural residues such as straw, cornstover, switchgrass, etc.

My wondering based on John's above, is whether there is much need for heat in Spain, and if so, if rocket-stove technology could be harnessed in burning those stones.

This is a technology that needs to migrate to Palestine as well.

I know of someone around here using rocket-stove technology to heat cob benches before venting exhaust.

Harvesting presently wasted heat is a topic that interests me.

Extending the growing season and cooking are other possible uses for waste heat.

The fermenting process itself generates heat. If you properly mix your nitrogen and carbon sources, you can get a good 150-160, which effectively
pasteurizes food for fragile populations. I know a guy who heated all the water his 5-person family used for 18 months this way.

Coppice wood from pruning is another source.

Seed-coat digesting enzymes are also present in mash from the fermenting process, and mash forms a safe pre-emergent herbicide for that reason, although it's higher use is often as animal feed.

Animals fed with mash are so healthy that the Bureau of Alcohol, Tobacco, and Firearms often visits the farmers whose animals win prizes at county fairs, a reason some of the best animals may not show up at county fairs any more.

We really need to get going on sensibly using surplus as resources that were formerly thought of as waste.

We can rehabilitate our image around the world by ceasing to throttle back production to elevate prices.

The better choice would to to share left-overs and how-to's and let prices be accessible to wider markets. The current deflation is sort of doing that. Places like MIT that share information so as to find the most innovative minds around the world have long benefited from sharing.

In some respects, it is fortunate that bad renewable products haven't so far been subsidized too much. The present oil-price manipulations are going to cut some knees off, but not as many.

Another approach to solve the problem of the olive stones is to ferment them anaerobically to make methane gas. This is due to the paste form of the pits. By this way, the energy used in the generation of high-pressure hot water can be saved.
Since the yield of the ethanol produced by the process mentioned above is relatively low, can it be justified economically ?

The HHV (higher heating value) of ethanol is 29.8MJ/Kg and I have found an article which quotes the HHV (higher heating value) of the stones as 17.7MJ/kg, (sounds about right) and on this basis the energy in 5.7Kg of ethanol represents about 9.6% of the energy in the original 100Kg of stones, not particularly good return but it gets worse. My guess is that the ethanol will end up as petrol substitute, in a car with a T2W (tank to wheel) efficiency of about 25% (combined town/highway cycle) so the final energy yield is about 2.5% of the original feedstock.
Alternatively, burn them any other way to produce electricity, even straight burning in a biomass power station should convert at least 35% to electricity. Now use this to run BEV's (battery electric vehicles) operating at 80% T2W efficiency and the combined efficiency is 28%, over eleven times better than the ethanol route!!
In general I would say that bioethanol production is a poor use use biomass energy resources if it ends up in the fuel tanks of cars.

You need to digest 100 kg of olive stones with enzymes in order to obtain sugars. Then you need yeasts to ferment the sugars and obtain 5.7 kg of ethanol.
What is the final cost of such an ethanol?
To obtain a cheap ethanol by that way you surely need new robust enzymes and new robust fermentors.
I never heard current enzymes and current fermentors are cheap.
I heard of people overcoming chemical production of ethanol by producing it biotechnologically, spending ten dollars of enzymes to obtain one dollar of ethanol. An academic exercise. Having money to burn, it is easy to do everything, even fabricate natural diamonds.

Ms Saunders mentioned above quite corrently:

"Animals fed with mash are so healthy that the Bureau of Alcohol, Tobacco, and Firearms often visits the farmers whose animals win prizes at county fairs, a reason some of the best animals may not show up at county fairs any more."

Perhaps if we fed our animals highly nutrient dense mash around the globe before slotter, we would have a lower incidense of heart attacks and strokes around the world; especially in the US. "You are what you eat, not what you don't eat." Indisputable logic.

Oh well,...we're just complacent Americans, we don't care about anything but our couches and our T.V's. probably because our food stocks provide so little nutrient density unless we pay ten times more for our meals at health food stores; or spend half a life time studying nutrition. Here's to long shelf live and dead food! Yeeeaaah!

Where are my potatoe chips?!