Phased-Sequenced Anaerobic Digestion by SKILLICORN Technologies
How Phased-Sequenced Anaerobic Digestion creates synergies and adds value to advanced, innovative waste treatment
The STL Anaerobic Digester (AD) changes the paradigm. Advanced AD systems now available commercially, place increasing stress on pretreatment: enhancing physical reduction of inputs and improving lysis. Varying approaches – physical, hydrodynamic, sonic, thermal and chemical – seek to render diverse inputs more easily digestible. What is not done, however, is optimization of the AD process itself. With few exceptions, all existing commercial AD systems still employ either a single or two-phase reactor in which all the sequential steps of anaerobic digestion are undertaken in an inefficient batch mode: hydrolysis, acidogenesis, acetogenesis and methanogenesis. Influent pretreated sludge passes all the way through the system, coming out the other end as a thick, foul smelling, poorly digested soup. Some companies are working to render the sludge to a “fertilizer” package, but market acceptance has been minimal. Only Milorganite, which is marketed by the City of Milwaukee, has gained any level of market acceptance.
The STL AD system parses the entire process, optimizing each phase along the way. Pre-treatment, strictly 3rd party, is optimized to the various input streams employed. Care is taken to ensure complete and cost-effective material reduction and lysis and to ensure that what passes through the system effects a correct C/N ratio (25 to 30). The STL hydrolysis sub-system is, itself, phased – breaking down inputs like egg yolk, for instance, instantly, and “working” more recalcitrant volatile materials like wood or paper, sometimes for months. The objective of the STL hydrolysis system is to break everything down to the point where inert minerals reform as grit, which being relatively heavy, is easily differentiated and withdrawn continuously from the system. What passes from the hydrolysis array to the acidogenesis reactor is a clarified, highly nutrified fluid. The acidogenesis reactor and subsequent acetogenesis and methanogenesis reactors are all up-flow reactors featuring STL’s unique “carbon-donor biofilm.” pH and temperature are set precisely to favor the specific anaerobes that effect the intended sub-process of any given reactor.
This highly optimized sequenced anaerobic digestion process ensures that the STL AD system is dramatically more efficient than all other systems now being marketed internationally, producing: little sludge (sic: mineralized grit), more nutrients, more biogas and much better biogas (sic: less CO2). This enhanced biogas is then subjected to a final bacterial methanation process which uses a virtually identical carbon-donor biofilm reactor and marginal inputs of hydrogen to convert residual CO2 to CH4, which is then compressed for storage and subsequent deployment as input to a fully integrated CHP (combined heat and power) process that is constructed around an array of micro gas turbines.
The final clarified nutrient-rich discharge may then be employed as technically “organic” inputs to the full spectrum of hydroponic and more mundane agricultural processes. Given market acceptance, it can also be packaged and sold at a significant premium as organic fertilizer.
The STL AD system parses the entire process, optimizing each phase along the way. Pre-treatment, strictly 3rd party, is optimized to the various input streams employed. Care is taken to ensure complete and cost-effective material reduction and lysis and to ensure that what passes through the system effects a correct C/N ratio (25 to 30). The STL hydrolysis sub-system is, itself, phased – breaking down inputs like egg yolk, for instance, instantly, and “working” more recalcitrant volatile materials like wood or paper, sometimes for months. The objective of the STL hydrolysis system is to break everything down to the point where inert minerals reform as grit, which being relatively heavy, is easily differentiated and withdrawn continuously from the system. What passes from the hydrolysis array to the acidogenesis reactor is a clarified, highly nutrified fluid. The acidogenesis reactor and subsequent acetogenesis and methanogenesis reactors are all up-flow reactors featuring STL’s unique “carbon-donor biofilm.” pH and temperature are set precisely to favor the specific anaerobes that effect the intended sub-process of any given reactor.
This highly optimized sequenced anaerobic digestion process ensures that the STL AD system is dramatically more efficient than all other systems now being marketed internationally, producing: little sludge (sic: mineralized grit), more nutrients, more biogas and much better biogas (sic: less CO2). This enhanced biogas is then subjected to a final bacterial methanation process which uses a virtually identical carbon-donor biofilm reactor and marginal inputs of hydrogen to convert residual CO2 to CH4, which is then compressed for storage and subsequent deployment as input to a fully integrated CHP (combined heat and power) process that is constructed around an array of micro gas turbines.
The final clarified nutrient-rich discharge may then be employed as technically “organic” inputs to the full spectrum of hydroponic and more mundane agricultural processes. Given market acceptance, it can also be packaged and sold at a significant premium as organic fertilizer.