Having done more research into this, I think my idea is is viable. It all depends on preparing it right and pressing the briquettes for maximum efficiency. It seems the Torrefaction process is vital if you want to obtain the maximum energy density. Below is an interesting study which concludes:
https://www.researchgate.net/public...olid_fuel_qualities_and_combustion_properties
"it was seen that the characters of the biomass fuels begin to resemble those of low rank coals in terms of the van Krevelen coal rank parameter. In addition, the results indicate that the volatile component of biomass is both reduced and altered producing a more thermally stable product, but also one that produces greater heats of reaction during combustion."
Having had email correspondence with a few academics in this area, most seem to think that my land is more than enough to provide 100% of my heating needs, as long as the straw is properly processed. One reply is below:
" Using a very simple torrefaction technology it is possible, however, to convert about 80% of the straw into biochar. The exact figure depends naturally on the type of straw and the conditions of the treatment. The calorific value of the biochar is about 20 MJ/kg. The straw needed to heat a 3 bedroom house will depend on the average temperature in your place in Scotland, which can be very low, I guess. Assuming an average temperature of 32°F and a total area of, say, 100 m2, then the amount of straw required can be easily calculated. Roughly speaking you would require about 3500 kg of straw per year, or about 7800 pounds. "
From what I can gather, average straw yields be acre is between 1000kg and 1500kg. Therefore it leaves me plenty of land left over to do other things with.
I think it looks viable and I will start the experiment this year. Lets see if It can provide 100% of my heating needs this winter. I understand it may be a lot of work, but my philosophy is to be as self sufficient as possible, so convenience or cost are not my motivators.