Seite - 132 - in Water, Energy, and Environment - A Primer

othersecond-generationbiofuelcrops.It isestimatedthatgrowing enoughalgaetoreplaceallUSpetroleumfuelswouldrequireonly 0.4%(15,000squaremiles)oftheUSlandarea,orasmallfraction of the landcurrentlydevoted tocornproduction.Algaecropsalso have a short harvesting cycle – 1 to 10 days – and so can be harvested repeatedly inashort time-frame. The biggest barrier to greater use of algae-derived biofuels is the cost of scaling up to commercial production levels. Another concern, for open-pond algae facilities, is contamination by invasive algae andbacteria and vulnerability ofmonocultures to viral infection. Many schemes for reducing costs and potential contamination are being explored, given the large potential markets available. One obvious target is ground transportation. Another suchmarket is theUSmilitarywhich is already testing biofuels in aircraft and ships. A third large potential market is commercial air transportation. Finally, like all energy sources, biomass has environmental impacts and risks – for example, water demand, and deforestation if land is cleared for biomass production. 8.5.5 Biochar Biochar is a formofcharcoal that is createdbypyrolysis (low-or no-oxygenheating)ofbiomass. It isbelieved thatpre-Columbian Amazonians used biochar to increase soil productivity. In addition, biochar has attracted growing attention because of its ability to sequester carbon for centuries (and thus reduce global warming) and its ability to attract and retain water because of its porous structure and high surface area. Its production also does not competewith foodproduction. 8.5.6 The future In my view, and that of many others, biomass will be a major part of our renewable energy future. It is available worldwide, grows in great and diverse quantity, can be used for direct Water,Energy, andEnvironment–APrimer132