Burning Toxic Plants for Green Energy

Burning Toxic Plants for Green Energy

Burn­ing Tox­ic Plants for Green Ener­gy:
The Merg­ing of the Phy­tore­me­di­a­tion and Bio­mass Ener­gy Crop Industries

In Sep­tem­ber 2002, researchers from Belarus pre­sent­ed a paper at the BioEn­er­gy 2002 con­fer­ence in Boise, Ida­ho, proud­ly mak­ing the U.S. audi­ence aware of their project pro­duce “renew­able” ener­gy from burn­ing trees that have been used to suck up radioac­tive Cesium-137 and Stron­tium-90 from Cher­nobyl fall­out. See: Fea­si­bil­i­ty of Appli­ca­tion of Short Rota­tion Wil­low to Reme­di­a­tion of Con­t­a­m­i­nat­ed Land.

For an update on this, see the Bio­fu­els could clean up Cher­nobyl ‘bad­lands’ arti­cle in New Sci­en­tist (6/27/2009). The arti­cle explains that: “The heavy radioac­tive residues [trees] will be burned in a pow­er sta­tion, pro­duc­ing a con­cen­trat­ed ‘radioac­tive ash’.”

Unfor­tu­nate­ly, this isn’t a new con­cept to U.S. “bio­mass” researchers, since sci­en­tists are Flori­da have already been work­ing hard to jus­ti­fy burn­ing trees that have been used to suck up arsenic from land con­t­a­m­i­nat­ed by wood treat­ment chemicals.

The fol­low­ing report doc­u­ments efforts by Uni­ver­si­ty of Flori­da sci­en­tists to merge the phy­tore­me­di­a­tion indus­try with the bio­mass ener­gy crop indus­try. This means that trees grown on lands con­t­a­m­i­nat­ed with tox­ic chem­i­cals like arsenic (referred to below as “As”) could be burned in coal-fired pow­er plants as “bio­mass” and would be con­sid­ered “green, renew­able ener­gy,” despite the fact that arsenic (or oth­er tox­ic chem­i­cals in ques­tion) would be redis­trib­uted to the envi­ron­ment through air emis­sions and ash disposal.

From “Annual Report for Biomass Programs of the Center For Natural Resources 2000–2001”

http://snre.ufl.edu/pubsevents/files/Biomass%2000–01%20Report.pdf

p9
“Recent research con­duct­ed by the SFRC has focused on the devel­op­ment of Short Rota­tion Woody Crops (SRWC). Species such as Pop­u­lus and Euca­lyp­tus are cur­rent­ly being improved by selec­tion and breed­ing to increase bio­mass pro­duc­tion. Although the aim of tree improve­ment is to devel­op feed­stocks for ener­gy pro­duc­tion, mulchwood, and pulp­wood, the objec­tive of increas­ing yields also com­ple­ments phy­tore­me­di­a­tion research objec­tives, because in the absence of hyper­ac­cu­mu­lat­ing trees, increas­ing yields poten­tial­ly result in increased con­t­a­m­i­nant removal. Fur­ther­more if the tree species, plant­i­ng tech­niques, har­vest­ing tech­niques, sil­vi­cul­tur­al options, etc. are the same for bioen­er­gy pro­duc­tion and phy­tore­me­di­a­tion, not only will this reduce phy­tore­me­di­a­tion devel­op­ment costs, but also increase the abil­i­ty to uti­lize crops grown on con­t­a­m­i­nat­ed sites as feed­stocks to the ener­gy, mulch, and paper industries.”

p10
“How­ev­er, unlike hyper­ac­cu­mu­la­tor, the plant tis­sue con­cen­tra­tions found in CW [Cot­ton­wood] were con­sid­er­ably low­er than the con­cen­tra­tion required to clas­si­fy the plant tis­sues as tox­ic waste accord­ing to the tox­ic char­ac­ter­is­tics leach­ing poten­tial (TCLP). There­fore, CW grown on CCA con­t­a­m­i­nat­ed land would not require spe­cial­ist treat­ment or dis­pos­al and may pro­vide an income for the landown­er in com­bi­na­tion with a grad­ual cleanup of the site.”

p50-51
When con­sid­er­ing plant­i­ng den­si­ty, har­vest fre­quen­cy must also be con­sid­ered. To max­i­mize the cov­er­age of root sys­tems, and poten­tial­ly increase the amount of soil receiv­ing phy­tore­me­di­a­tion treat­ment, it may be ben­e­fi­cial to plant at very high den­si­ties. How­ev­er, at high den­si­ties, trees rapid­ly com­pete with each oth­er for light, as leaves over­lap and block out light reach­ing the low­er canopy dur­ing canopy clo­sure. When canopy clo­sure occurs, the con­ver­sion effi­cien­cy of light into bio­mass is great­ly reduced. Severe com­pe­ti­tion between trees for light and nutri­ents can result in self-thin­ning where­by the small­er trees receive too lit­tle light to sur­vive and the den­si­ty of the plan­ta­tion is reduced. Since bio­mass pro­duc­tion is a dri­ving force con­trol­ling uptake of con­t­a­m­i­nants, high den­si­ties may there­fore lead to a reduc­tion in the effi­ca­cy of phy­tore­me­di­a­tion. Har­vest­ing has the effect of open­ing the canopy to light and since har­vest­ed trees often gen­er­ate mul­ti­ple stems, har­vest­ing can great­ly increase the rate of bio­mass pro­duc­tion. How­ev­er har­vest­ing can also result in increased mor­tal­i­ty, due to the intro­duc­tion of infec­tion into the cut stump, and there­fore har­vest fre­quen­cy should not be too high.

Thus, plant­i­ng and har­vest­ing rec­om­men­da­tions for a cot­ton­wood phy­tore­me­di­a­tion sys­tem need to be a com­pro­mise between max­i­miz­ing soil cov­er­age by plant­i­ng at high den­si­ties and plant­i­ng at low­er den­si­ties to avoid ear­ly canopy closure.

Plant tis­sue con­cen­tra­tions observed at Archer and Quin­cy were well below the lev­els required to clas­si­fy the plant tis­sues as tox­ic waste accord­ing to the Tox­ic Char­ac­ter­is­tics Leach­ing Poten­tial (TCLP). For exam­ple, the high­est tis­sue con­cen­tra­tion observed at either site was 6.7‑mg kg ‑1 . The TCLP test method requires that waste sam­ples be extract­ed with an amount of flu­id equal to 20 times the weight of the sol­id phase. Even if all As in the tree tis­sue con­tain­ing 6.7 mg kg ‑1 was leached out to the extract­ing flu­id, the max­i­mum pos­si­ble As extract con­cen­tra­tion would be 0.335 mg l ‑1 , sig­nif­i­cant­ly low­er than the TCLP stan­dard for As of 5 mg l ‑1 . There­fore, cot­ton­wood bio­mass grown on As con­t­a­m­i­nat­ed soil should not require statu­to­ry treat­ment or dis­pos­al as haz­ardous waste and may be dis­posed of in a munic­i­pal land­fill or used for pulp, mulch or ener­gy production.