Arb arisings as a potential wood chip biomass fuel source?

[dgcunningham]

Hi guys. I'm pretty inexperienced at posting on this forum although I have been visiting here for some time now. I get the impression that you are a friendly bunch and don't mind sharing your knowledge with the less experienced of us out there. On that point, I have a question and think you guys could help shove me in the right direction.

 

I am currently involved in setting up a tree station in Manchester. Greater Manchester Tree Station (GMTS) is a social enterprise and hopes to operate as a hub of silvicultural ventures within the city, involving practicing coppice workers, social foresters, arborists and woodworking artisans of all denominations. In short, if you like wood you're in!

 

We are currently researching potential avenues for converting arboriculture arisings into a usable biomass fuel source. In particular, I am trying to compile a feasibility study on the conversion of arb industry wood chip into a fuel source for wood chip boilers.

 

It would be great to hear from anyone who has endeavored to accomplish this and learn from their findings. Better still, it would be great to hear from anyone who has accomplished it! Obviously they are numerous factors contributing to the difficulty of this conversion, moisture content, chip grade specifications and foliage content but, there may be less obvious ones. It would be really helpful for us to hear your opinions on this.

 

Any info would be greatly received and if anyone can link me to other forums of a similar nature that would be handy too.

 

Regards David.

[Justme]

Wont the chippings be too wet?

 

Especially if you are getting paid by the output kWh.

 

A mate has just set up doing wood chip but they are buying in dry wood to chip. They are still charging by the volume but are just about to change over to output kWh once they can agree a rate with the buyer.

 

Seems an odd way of doing the billing to me as they get paid for the actual energy going into the heating system not the energy that goes into the burner. As the best I can see the system running at is 80-85% they loose 15-20% best case & prob more like40% worst case. So if the system is running badly due to lack of servicing or just how its set up & used they get paid less. Cant see any other utilities charging by the unit less the efficiency of the equipment you use.

 

 

What would be a fair price for delivered chip per

 

m3

tonne (at a specified moisture content)

kwh delivered (would incur test costs)

kwh out put as measured by the burners meter

 

All inc delvery costs

[renewablejohn]

Quite an easy operation. Start with arb arisings in excess of 50% moisture content dry to less than 25% moisture. Grade chip to G30 or similar spec for biomass boiler. Recycle the fines and reduce moisture content down to between 8-12% then produce wood pellets and briquettes.

 

Simples

 

Did I forget to mention the 150k investment in machinery (And thats cheap using second hand machinery)

[dgcunningham]

Hi Justme, thanks for the reply and the input.

 

We currently charge by the kWh going into the heating system. Its a good point you made about the efficiency of the system and it is a difficult problem. We see it as a short term sacrifice to establish a client base. Its a chicken and egg situation, people are reluctant to supply as there is not the demand and people are reluctant to install an efficient ( expensive) system as the suppliers are not out there.

 

One thing we can be sure of though is that the big utility providers are putting the price up. We have a huge natural resource within our green spaces, it is estimated London provides over 60,000 tonnes of arb arisings per annum and alot goes into land fill. As a nation we import over 50,000 tonnes of charcoal a year. Crazy!

 

The fundamental problem is that we are in effect competing with the large utility providers with an established infrastructure and those markets set the the kWh price. As a supplier we need to be providing fuel at around 3 pence per kWh (including delivery) so the clients will even begin to consider it. We are managing this but as yet still buying a lot of timber in.

 

Regarding the 'greeness' of the wood chip from arb arisings it is a valid point. We are researching ways to reduce the moisture content in wood chip piles through ventilation systems or combining recycled wood products (tests under way). We are lucky to have a Ba (hons) Arboriculture student dedicating his dissertation to the subject.

 

One step at a time though, my task is less concerned with moisture content (which is the big problem) but rather research the feasibility of utilising arb woodchip and try to identify other problems which might come to light and discuss ways of combating them. What we need to find is a way of producing a wood chip boiler grade product from an industry bi-product, then we can effectively compete with the utility providers.

 

Like I said in the original post, this is just a feasibility study and you guys are a great resource for that.

 

David.

 

Ps. please keep the input coming!

[dgcunningham]

Hi renewablejohn.

 

Thanks for the input.

 

Have you experience of converting arb arisings into wood chip fuel? If so, i would love to have a chat with you.

 

We're not going down the route of pellets or briguettes. Is that more applicable for domestic use and somewhat more difficult to convert? We are targeting medium sized civic clients, people like local authority authority buildings, multiple occupancy residencies, swimming pools, schools etc.

 

David

[renewablejohn]

Hi Justme, thanks for the reply and the input.

 

 

 

 

Regarding the 'greeness' of the wood chip from arb arisings it is a valid point. We are researching ways to reduce the moisture content in wood chip piles through ventilation systems or combining recycled wood products (tests under way). We are lucky to have a Ba (hons) Arboriculture student dedicating his dissertation to the subject.

 

 

David.

 

 

 

If you use ventilation systems to reduce your moisture content you will find that fungal spores are encouraged some of which are deadly to humans. We have found rapid drying of the arb arisings in a solar kiln minimizes the growth of these fungal spores. In respect of mixing arb arisings with recycled wood products this would then restrict the type of appliance able to burn the product to waste incineration directive approved boilers which can be twice as expensive as a virgin timber boiler.

[renewablejohn]

Hi renewablejohn.

 

Thanks for the input.

 

Have you experience of converting arb arisings into wood chip fuel? If so, i would love to have a chat with you.

 

We're not going down the route of pellets or briguettes. Is that more applicable for domestic use and somewhat more difficult to convert? We are targeting medium sized civic clients, people like local authority authority buildings, multiple occupancy residencies, swimming pools, schools etc.

 

David

 

Exactly the same people we targeted who were not interested in woodchip as the density of the material made transport and handling difficult. A lot of authorities are replacing their coal boilers for "green" pellet boilers or log boilers hence our production of pellets and briquettes. Long term we will be producing torrefied wood pellets from arb arisings allowing the local authorities to have a green solution whilst retaining their existing coal boilers.

[dgcunningham]

Thanks for the heads up on the toxic fruiting fungal spore potential and the advice on the solar kiln process. I'll pass the info on to the moisture content guy.

 

I appreciate the difficulties encountered with the haulage and handling logistics with wood chip as opposed to pellet transport. We've already fallen foul of a 'inappropriately' placed fence post but as yet people haven't been dismissive of using wood chip. Maybe something we should certainly keep in mind as a potential future problem.

 

Which area of the country are you based renewablejohn?

 

I must confess i'm unfamiliar with torrefied pellets.

 

The torrefied pellets, are they produced from saw dust sized material? Will you further process the arb sourced chip to achieve the grade? In fact, is this something you are currently doing to produce wood pellets?

 

Just briefly looking into the process it doesn't seem dissimilar to charcoal, amazing calorific value 21 MJ/Kg thats double wood chip and hydrophobic!

 

Are there many people producing these in the UK?

 

Thanks for the info renewablejohn!

 

David

[renewablejohn]

Thanks for the heads up on the toxic fruiting fungal spore potential and the advice on the solar kiln process. I'll pass the info on to the moisture content guy.

 

I appreciate the difficulties encountered with the haulage and handling logistics with wood chip as opposed to pellet transport. We've already fallen foul of a 'inappropriately' placed fence post but as yet people haven't been dismissive of using wood chip. Maybe something we should certainly keep in mind as a potential future problem.

 

Which area of the country are you based renewablejohn?

 

I must confess i'm unfamiliar with torrefied pellets.

 

The torrefied pellets, are they produced from saw dust sized material? Will you further process the arb sourced chip to achieve the grade? In fact, is this something you are currently doing to produce wood pellets?

 

Just briefly looking into the process it doesn't seem dissimilar to charcoal, amazing calorific value 21 MJ/Kg thats double wood chip and hydrophobic!

 

Are there many people producing these in the UK?

 

Thanks for the info renewablejohn!

 

David

 

Based just outside Bolton

 

Torrefied wood we can produce direct from arb arising once it is torrefied it becomes more friable and easier to pelletise than normal wood pellets with the added advantage that it is hydrophobic.

I dont know of any UK manufacturers only Dutch and Canadian

[BCF]

Large piles of woodchip get pretty hot whilst drying, any danger of spontaneous combustion.