For illustrative purposes, assume that a tree has a lifespan of 100 years.

The tree absorbs more carbon dioxide as a mature tree and less as a sapling or when it is old.

Years	CO2 Absorbed / Year	Total CO2 Absorbed	Total
0-10	1	10
10-50	5	200	210
50-70	5	100
70-100	3	90	400

One form of math: After 50 years the tree has absorbed 210 units. The tree is chopped down and burned, releasing the 210 back into the atmosphere. 

The tree is replaced with a new tree which in the next 50 years absorbs 210 units
from the atmosphere.  

Since 210 was chopped and 210 planted, they cancel out over a period of 100 years and the operation is net-zero.

The second form of math: If nothing happened then 400 units would be absorbed over 100 years, but because of the tree operation only 210 was absorbed resulting in a loss of 190. 

In addition, the tree operation involved diesel farm equipment, transportation fuels, and wood chipping. Thus, the loss is much greater than 190. 

This is called net-zero because it sounds good, and besides, the term isn`t defined.

The third form of math: A biomass company signs a contract with an electric utility to produce tree-based electricity. 

In addition to the second form of math, the biomass company claims that it signed unknown contracts with unknown companies to plant unknown trees in unknown places. 

The biomass company claims that a plan exists, but there is no oversight, monitoring, or evaluation of any
actual planting by any regulatory agency or any public review. 

This is called net-zero perhaps because it takes an IQ of zero to believe that a litigant-oriented, greed-based company, that relies on public relations to persuade regulators, should be trusted.