AP proposes to control the level of atmospheric CO2 by growing biomass to remove it, converting the green biomass by anaerobic digestion to methane and concentrated carbon forms for segregation, using the methane beneficially and segregating the carbon to keep it out of the cycle. Sugarcane is the most efficient CO2 converter now known, so it is used in the example below; USDA yield of 40 dry tons/acre-year (DT/AY) is raised to 50 for AP, reflecting inclusion of leaves, tops and green trash. Four levels of digestion 50-80%, are used to calculate how much area of cane is needed to stabilize CO2 level at present emission rate if carbon forms are actually segregated, and how much methane we get from the process.
| 1 | Digestion of biomass, wt% | 50 | 60 | 70 | 80 |
| 2 | Total digester gas, mcf/AY | 736 | 883 | 1030 | 1177 |
| 3 | Methane (70%), mcf/AY | 515 | 618 | 721 | 824 |
| 4 | CO2 (30%), mcf/AY | 221 | 265 | 309 | 353 |
| 5 | Digester residue, DT/AY | 25 | 20 | 15 | 10 |
| 6 | Carbon content (45%), DT/AY | 11.25 | 9 | 6.75 | 4.5 |
| 7 | Weight CO2, DT/AY | 13.53 | 16.23 | 18.94 | 21.64 |
| 8 | Carbon content of CO2, DT/AY | 3.69 | 4.43 | 5.17 | 5.90 |
| 9 | Segregated C (SC), DT/AY | 14.94 | 13.43 | 11.92 | 10.40 |
| 10 | SC Avoidance (SC/0.6, DT/AY | 24.90 | 22.38 | 19.87 | 17.33 |
| 11 | Methane credit, , DT/AY | 4.64 | 5.57 | 6.50 | 7.43 |
| 12 | Total Avoidance (TA), DT/AY | 29.54 | 27.95 | 26.37 | 24.76 |
| 13 | Needed for 4.4x109 tons, 106 acres | 149 | 157 | 167 | 178 |
| 14 | Total Methane, 1012 cf/year | 76.7 | 97 | 120 | 147 |
The calculation of line 10, converting segregation to avoidance by dividing by 0.6, reflects the fact that only 60% of emitted CO2 stays in the atmosphere, the rest being removed by natural processes; thus, removing 60 units is equivalent to not emitting 100. Methane credit stems from substituting methane for coal and air, emitting less CO2 for a given energy release; it is assumed here that coal and oil are replaced on an equal energy basis. Line 13 assumes the emission avoidance of 4.4x109 tons of C annually stabilizes CO2 level at current value. Expressing AP results as avoidance, we can calculate the area of cane crop needed to stabilize CO2 level, and line 14 indicates methane yield. It is seen that AP can indeed do the CO2 control job completely, without restricting emissions from from substituting methane for coal and oil. At the same time, a large amount of methane becomes renewable fuel.
In the plot below, the level of CO2 in the atmosphere over the next century is shown under five conditions:
- Case A - doing nothing
- Case B - maintaining a constant 1990 emission rate
- Case C - applying AP as calculated in the example uniformly over the span of 100 years (adding 1% of line 13 incrementally each year to the AP program);
- Case D - applying AP over 50 years (2%/year)
- Case E - the same in 20 years, or 5% of line 13 per year.
This plot applies to all the examples as long as the calculated area of 4.4x109 tons, 106 acres is engaged.
It is apparent that Case A leads to high CO2 levels; it can be estimated that this curve would probably flatten out by the next millennium somewhere above 900 ppm through natural removal mechanisms such as ocean solution, biomass increases, peat formation, etc. Case B is a less severe version, with equilibrium reached over some longer time span than Case A. The AP Cases C-E offer some hope of real affordable control of CO2 level at much lower values while providing much renewable clean, cheap energy and helping with many other problems facing the world.
The significance of Greenhouse Warming (GW) due to CO2 can be argued, but the fact that it is a reality seems to be beyond question. It was early on invoked to explain why the Earth is warm enough to develop and sustain the life it does. All that apart, AP provides an economic basis to do something with CO2 that makes a fossil fuel renewable at very low cost, and for this reason alone it should be examined critically, regardless of any other considerations.
