It sounds like composting it would be a good idea. I don't know what the nitrogen content is, but if it's said to be 'too rich' to use as mulch, perhaps it is on the 'green' side. That suggests mixing it with some wood chips, but not very many as they are a strong brown. The eelgrass may help fluff the mixture as well, and compost is best with the largest number of diverse ingredients.

This article:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2619652/

suggests it is phytotoxic, in other words it inhibited growth of new plants, when mixed directly into soil. Further support for composting it first.

This article:
http://www.ncbi.nlm.nih.gov/pubmed/19467866

was a composting study using added urea to boost the C:N to 25 or 30 to 1. This suggests olive pomace is on the BROWN side to start with, so my suggestion above to add wood chips is out the window unless you have some high nitrogen greens to balance them out. Maybe the eelgrass. The wood chips would be great for fluff though, which is important with something pasty like this.

I hope this helps, I'm now a 5-min olive pomace expert thanks to Google. Not!

Apparently what to do with this pomace has piqued the interest of some and there is research now to determine what is the best use of this material. The linked article indicates that composting it, and adding other materials, is a good use.

Here is a link that might be useful: Olive pomace composting

Thaanks guys, for the replies and informative articles. I posted becuase our attempts at composting pomace result in something that looks like soaked particle board. (Or particle board with eelgrass mixed in.) I'm hoping somebody here's actually had good luck with backyard composting of the stuff. On the other hand, maybe there wouldn't be som many research article on how to compost pomace if it was easy to do...

Can you describe the composting process you tried, i.e. how much of which ingredients, size of the pile, whether it heated, odors or other observations, how long did it you let it cook, was it turned, what time of year...etc. Maybe we can help you diagnose.

Off the top of my head it sounds like maybe a nitrogen deficiency in the pile. So more greens. But if you can give us some more detail we will probably have better answers.

Josko - Can you use it as animal feed? As a 10% supplement it's been used in finishing pigs and lambs. More than 10% and the high phenol quantities could cause problems.

But it spoils quickly, so unless you can dry it, make silage of it (lactic acid fermentation), or have a huge herd of pigs to fatten, it will mold and that's not good.

For composting it, it's high moisture and would need to be mixed with something fairly dry like straw or wood shavings, and turned frequently. Layering it with straw and turning it with a plow might work for mixing such large quantities.

I found only one analysis of it as a fertilizer, and it's not as high nitrogen as some things like chicken manures.

Olive Pomace: 1.15/0.78/1.3 (NPK?)

Ask the local agricultural college to get a grad student to do some field testing for his or her degree research ... how does it work as a tilled-in supplement? How much can you add - how many CM/year? Can fields be planted immediately, or do they need to be left for a month or two or longer?

If you can spread it as it comes from the presses and till it in to decompose in the fields that would be ideal. It's less work and less expense.

Thinking back to some avocado processors in Mexico that have large quantities of avocado peels and seeds left ... they crush the seeds for high-grade cosmetics oil, then use the pomace and peels for pig feed, then use the pig manure on the avocado orchards. However, they harvest year-round so they don't have tons of material one month and none the next.

GOT ONE!
http://perso.wanadoo.es/japsm/jose/images/documentos/Biocycle0610.pdf

Operators create an **optimal mixture** of olive mill pomace and structural raw material (generally other by-products such as olive leaves, olive branch clippings and soil remains, straw and manure). [NOTE: The "structural material" keeps the pomace from making bricks ... you need fibrous material more for that than any nutrient balancing.

The facilities utilize a low cost windrow system on a
concrete hard surface with dump loader, turning once per month during the four to seven months of composting phases and two to three during the curing phase. The whole process takes 6 to 10 months and is fully integrated into the olive oil growing and processing season.

===============
Looking at the pictures of a similar "windrow" system in Brazil, the piles are long heaps about 5 feet tall and maybe 7 feet wide. There is enough empty space on one side for one new row ...

To turn them, they pick up a bucketful with a front-end loader and move it to the empty space, and just dumping it does the mixing ... move the whole row over. that leaves a new empty space ... move the next row.

===============
The remaining question is this: what is "optimal mix" ... and all your friend has to do is write to the authors of that scientific paper.

they'll be able to tell exactly what method they are using.

If it's so prone to turning into bricks, why not mix in some straw, cast it into bricks and build an Olive House? An abode made of Pomace Adobe! :-p

It does turn into 'bricks' or more accurately 'briquetes' because it burns when dry like you wouldn't believe. It starts out as a heavy paste and hardens as it dries.
Anyway, best results we've had is mixing it with chipped ramial Aleppo Pine, using only needles and branches Mixing it with animal by-products (fish scrap) went anaerobic, most likley because the paste is too dense for ventilating the pile. We also tried mixing it with sheep manure and that went anaerobic, too. So the suggestion above is that it's most important to combine it with a rough, porous material to prevent compaction is the key. The second step is to add some N. We haven't experimented with tubes, pipes, etc for areating the pile.
Only animals available in numbers locally are sheep and goats, and they won't eat it.

Sounds like you've tried a lot of good ideas and you're well on your way to sorting this out. The aeration might be helped by frequent turning as well, but you would almost have to do that with machinery if you're talking about tons of material. I like the perforate pipe idea too.

It does turn into 'bricks' or more accurately 'briquetes' because it burns when dry like you wouldn't believe. It starts out as a heavy paste and hardens as it dries.

I imagine that with the residual oil in there, as soon as the moisture content is gone it would burn really well.

Could this be pressed into small chunks, air dried, and used as renewable fuel? How smoky is it? Could you turn it into decent cooking fuel? Heating?

You could even do what the sawmills do here making wood pellet fuel, and burn part of the dried pomace to power a steam engine that powers the machinery that makes the briquets

I just don't think we have the quantity to set up a viable fuel business; house heating is solar-electric and working fine. We tried using it as a food grill fuel, and it found flames out too much and doesn't leave behind a bed of coals.
What we'd really like to do is minimize outlays for organic fertilizers for the olive orchard.

You would need a fibrous wood filler for fuel. I found another Spanish report on making fuel bricks or pellets from pomace and they were working with a sawmill to get sawdust and shavings and bark. Maximum of 50% pomace for fuel pellets gave best results.

Ask the Spaniards who wrote the paper on composting I linked to what the best ratio of fiber to pomace is for composting ... or try various mixes in test bins and see what works.

You have already tried 100% and know it doesn't work. If it's has the texture I think it does, composting would need at least twice as much straw or wood chips or shredded olive prunings as pomace to break up the paste. Try 50% and 30% pomace well-mixed into woodchips.

Use whatever is local and cheap or free. And in your case, things that won't mess up your organic certification.