text: The lack of equipment and structures needed to begin growing algae in large quantities has inhibited widespread mass-production of algae for biofuel production. Maximum use of existing agriculture processes and hardware is the goal.
  Closed systems (not exposed to open air) avoid the problem of contamination by other
  organisms blown in by the air.  The problem of a closed system is finding a cheap source of sterile .
  Several experimenters have found the  from a smokestack works well for growing algae. 
  For reasons of economy, some experts think that algae farming for biofuels will have to be done as part of cogeneration, where it can make use of waste heat and help soak up pollution.
  To produce micro-algae at large-scale under controlled environment using PBR system, strategies such as light guides, sparger, and PBR construction materials required should be well considered.