instalation, running costs and reliability are major challenges, with slurry based digesters, as we are working with a relatively large volume of low methane product on dairy farms, that are more comfortable looking after cows as AD plants, compared to industrial sized ones with specialist tech and dedicated labour! if anyone can crack this! and a few have tried and not been able to! there is a fine line, between building too cheap! and it failing! to over spec'ing it and it not being viable! OMNI have built x3 of these and i think ours is probably going the best, although it certainly hasn't been without its challenges! they are still learning no doubt, and thankfully still in business (ours is running nearly 5 years now ) and the way electric price is going, there may be a opportunity for many more if they can overcome these challenges! you mentioned earlier that it is a 50kw engine that your farmer has! so as you say it doesn't leave you much surplus, if you have big pumps! although ours doesn't run for long! is your farmer running on pure cow slurry? or is he adding anything dry? i expect the gas mixer wouldn't do much if too fiberous! am i right in saying you built your own? that would take a bit of doing wouldn't it! and not something we could all do! how is yours going? what are you feeding it? and what output are you getting?what make of engine? are you planning on developing them for others as well? sorry for all the questions! just interested to see success stories as there has been to many failures around!