The basic feedstock or required production capacities for various agricultural byproducts and livestock manure are listed here.
|Feedstock||Volume||Unit||Waste Name||Suggested Biogas Reactor Technology|
|Cassava||70||TPD of Starch||Wastewater||Mesophilic EGSB or UASB|
|Cassava||70||TPD of Starch||Pulp or Wetcake||Thermophilic CSTR|
|Cassava||40||TPD of Ethanol||Stillage||Thermophilic CSTR|
|Palm||30||TPH of FFB||POME||Thermophilic CSTR|
|Dairy, Cow||10,000||Head||Manure||Mesophilic CSTR|
|Dairy, Buffalo||13,000||Head||Manure||Mesophilic CSTR|
|Beef Cattle||15,000||Head||Manure||Mesophilic CSTR|
|Food Waste||100||TPD of Waste (at 12-15% TS)||Restaurant Disposal||Mesophilic CSTR|
|Sorted MSW||125||TPD of Waste (at 25-35% TS)||Kitchen Disposal||Mesophilic CSTR|
|Industrial||28||TPD of COD||Wastewater||Mesophilic or Thermophilic CSTR|
|Sewage||850||TPD (at 6% TS)||Surplus Activated Sludge||Mesophilic CSTR|
|Napier Grass||100||Hectare||Fresh Grass||Mesophilic CSTR|
It is of paramount importance to understand that in biogas reactor designs, there is no such thing as one-size-fits-all. Each feedstock needs to be managed differently and each needs different pretreatment before it goes into the digester. The criticality of pretreatment cannot be underestimated. Additionally, if the biogas is to be further utilized, then post-treatment is required, generally involving the reduction of hydrogen sulfide (H2S) and moisture. This can be easily managed with automated, properly sized and reliable scrubbers and dryers.
Furthermore, each plant needs to be sized differently if there are issues with seasonality of the feedstock. Proper design and optimization of the biogas plant size and type are keys to technical, commercial and financial success and project continuity.
In general, a mesophilic or thermophilic continuously stirred tank reactor (CSTR) steel tank design provides high robustness and reliability. Initial capital expenditures (CAPEX) maybe be higher, but in the long run, with a proper, safer, more efficient, more reliable and more robust design, the payback should be quicker and more consistent.