[Terrapreta] city and farm

[Sean K. Barry]

Hi Duane, Lou,

The point of using biomass for carbon based fuels and for carbon based energy production is that the resulting release of CO2 is not "new" carbon introduced into the atmosphere, from 300 million year old carbon in fossil fuels, but rather it is RECYCLED carbon which was taken from plants in the biosphere.  With enough plant growth, even CO2 emitted by burning fossil fuels may be taken up by the growing plants.
The difference between fossil fuels and biomass, is that biomass does not ADD to the amount of carbon already in the Biosphere.

Municipal solid wastes are not a good choice for a feedstock for charcoal to be used in agricultural soils.  This was discussed a couple weeks back.  Plastics make a substantial portion of the municipal solid waste stream.  Plastics do contain carbon and can be made into a form of charcoal.  However, plastics also contain many toxic chemical additives (plasticizers, hardeners, stabilizers, dyes, etc) that give the different types of plastics their properties for use.  These chemicals include poly-vinyl chlorides, fluorinated carbons, some heavy metals, and they decompose slowly , leaving toxic compounds that can pollute biological systems and water systems.  Halides and heavy metals are a big no-no for biological systems.

Plastics are so stable that attempting to pyrolyze them would release more carbon in the short term than could be sequestered if they were used rather to make recycled plastic products, or even if they were left as is and buried in waste disposal sites.  The recycled plastic product route at least avoids more of the potential for environmental contamination.

Regards,

SKB
  ----- Original Message ----- 
  From: Duane Pendergast<mailto:still.thinking at computare.org> 
  To: 'lou gold'<mailto:lou.gold at gmail.com> ; 'Terrapreta'<mailto:Terrapreta at bioenergylists.org> 
  Sent: Wednesday, November 14, 2007 9:32 AM
  Subject: Re: [Terrapreta] city and farm


              Very good point Lou,



  And it's not just the new "agrichar" technologies. The new emphasis on using biomaterials for ethanol and diesel fuel is being driven by the climate change issue mixed with the idea that it will improve energy security for the short term. The promotion of biofuels is based on the assumption that carbon dioxide released from biofuels will be re-reabsorbed by growing plants. That is not necessarily true. Even environmental groups are belatedly realizing these approaches may not greenhouse gas reducers in the long term, as forests are replaced with energy crops and the soil is mined for every bit of instant growth it can muster. It seems few are thinking through issues to sustainability of energy and food for long term security. Your suggestion of city-farm synergy makes much sense.



  Duane



  -----Original Message-----
  From: terrapreta-bounces at bioenergylists.org [mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of lou gold
  Sent: November 14, 2007 7:47 AM
  To: Terrapreta
  Subject: [Terrapreta] city and farm



  Hello All,

  I've been trying to confront the issue of whether the new agrichar technologies 
  will be directed primarily toward energy or toward restoring soil qualities. Isn't 
  this just a new version of the question of productivity vs sustainability? 

  The high tech discussion at the level of agribusiness seems to focus on using 
  agricultural wastes for more energy efficiency -- either integrated cogeneration 
  or producing more marketable fuel end-product. Profit/loss is based on a relativley 
  short term. Economics and ecology get separated. The result has not been 
  good for the earth. 

  Where did this separation come from? I suspect that it is because the farm and 
  the city got separated. As the technological reach of civilzation expanded so did 
  the dysfunctions production without sustainabilty. 

  Would it be a useful path to start considering how the logic of Terra Preta 
  might heal the city-farm separation? How? Perhaps by seeing the waste as located 
  in the city and thinking about turning this waste into an agrichar form that 
  would be sent back to the farm to restore the soil? Maybe it could be a modern 
  version of what was taking place in Amazonian Indian times.


  Might it be possible to reconnect city and farm ECOLOGICALLY? 

  What do you think? 


  -- 
  http://lougold.blogspot.com/<http://lougold.blogspot.com/>
  http://www.flickr.com/photos/visionshare/sets/<http://www.flickr.com/photos/visionshare/sets/> 

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