Burning of waste timber ecological or not?

speedyjoe

cepheus wrote: »

but by properly burying it you can effectively offset carbon production from other sources.

"properly" here would mean burying it in rock strata where it would release no carbon for millions of years - just as where the carbon in the fossil fuel resources would have stayed if they hadn't been exploited. This would of course be impossible. Burying wood where the carbon would not be locked up and so released within decades would in reality not offset anything.

cepheus

speedyjoe wrote: »

"properly" here would mean burying it in rock strata where it would release no carbon for millions of years - just as where the carbon in the fossil fuel resources would have stayed if they hadn't been exploited. This would of course be impossible. Burying wood where the carbon would not be locked up and so released within decades would in reality not offset anything.

This is not true, slowing down the rate of carbon release into the environment substantially reduces the rate of global warming. This is beneficial for several reasons. First the oceans and other natural sinks such as peat bogs and forests themselves have an ability to sequester carbon dioxide providing the rate of emission is not too high. Secondly any means to delay the rate of warming gives an opportunity for mitagation technologies or social changes to develop. Examination of wood from properly capped landfill many decades old suggests that it decays at a minimal rate in view of these other processes. Even paper which decays at a greater rate than wood can stay sequestered for long periods. In some cases early 20th century newsprint can still be read from dug up landfill. The capping, soil and climate is critical though.

However, one issue that I should have made clear, is that if the wood could be used in a boiler to offset coal or other fossil fuel emissions, this would also result in a net reduction in CO2. Of course this is likely to produce other toxic emissions unless the combustion is closely controlled. In practice wood cannot be used as efficiently as other fossil fuels due to various reasons.

Life_Goggler

Hi

All the answers have been pretty comprehensive, it's great to see all the knowledge on here.

Just to add that burning wood counts as a zero emission fuel because the amount of carbon dioxide it gives off when burned is offset by the amount that was absorbed when it was grown.

speedyjoe

cepheus wrote: »

This is not true, slowing down the rate of carbon release into the environment substantially reduces the rate of global warming. This is beneficial for several reasons. First the oceans and other natural sinks such as peat bogs and forests themselves have an ability to sequester carbon dioxide providing the rate of emission is not too high. Secondly any means to delay the rate of warming gives an opportunity for mitagation technologies or social changes to develop. Examination of wood from properly capped landfill many decades old suggests that it decays at a minimal rate in view of these other processes. Even paper which decays at a greater rate than wood can stay sequestered for long periods. In some cases early 20th century newsprint can still be read from dug up landfill. The capping, soil and climate is critical though.

However big do you think the landfills and forests to fill them would have to be to make any significant reduction in atmospheric carbon? And how efficient would the process have to be just to offset the carbon released from the fossil fuel used to facilitate the activity?

CO2 sequestration by pumping it into oil and gas fields is one thing but burying wood instead of burning it to harvest energy? That has to be one of the daftest ideas I have heard on this topic.

cepheus

speedyjoe wrote: »

However big do you think the landfills and forests to fill them would have to be to make any significant reduction in atmospheric carbon? And how efficient would the process have to be just to offset the carbon released from the fossil fuel used to facilitate the activity?

CO2 sequestration by pumping it into oil and gas fields is one thing but burying wood instead of burning it to harvest energy? That has to be one of the daftest ideas I have heard on this topic.

In the UK 109 sq miles (280 km2) - is now landfill about 0.1% of the UK land area. The amount of wood produced in the UK would increase the height of this area by around 5cm/year. Having a smelly waste tip producing methane next to your door is one thing, having treated wood is another. Perhaps you would prefer to breath in the copper arsenate and God knows what else used in the preservatives? Most of the waste timber could contain just about anything, they didn't really care 100 years ago.

It may not be necessary to actually bury it, but it has to be kept from rotting in some way and there are other options, unfortunately recycling isn't usually an economic or legal one in many cases due to fixings and preservatives. Ironically the wood wouldn't meet the required environmental standards!

The amount of roundwood produced (423 million tonnes carbon/year) is enough to offset the entire air and water transport emissions combined. This is small in relation to the total world emissions about 7.6 billion tonnes but is the most difficult part to deal with. However, the amount used for fuelwood is about 2 billion tonnes carbon mainly in developing countries for local fires & cooking. This is not net of course. I think there is more being grown in forests than burnt due to deforestation, but there is contradictory information about this.

If wood can be economically burned for heat and power fine. Don't forget it is much less dense than coal and tougher to cut up. All this takes energy. It is possible to mix it with coal in a power station, they will take about 5% before you start to get problems and it still reduces the efficiency of the station, partly due to the reduced temperatures caused by the oxygen content. However, there is no genuine economic way to do this, the government effectively subsidises green power because of renewable energy commitments. Without this the generating companies wouldn't touch it. There are other ways such as gasification but it is even more difficult to make these economic.

The problem is that everyone wants an aesthetically attractive solution but in the hard world of economics you have to consider all the options.