The original ICFPA/NCASI calculation tools consist of two parts: a report that describes the approaches for estimating greenhouse gas emissions from pulp and paper mills, and an Excel spreadsheet to aid in the calculations. It is intended that these industry-specific tools be used in conjunction with an accepted GHG accounting protocol such as the "Greenhouse Gas Protocol" issued by the World Resources Institute/World Business Council for Sustainable Development (WRI/WBCSD) or other accepted protocols for corporate GHG inventories. Originally released in December 2002, the calculation tools were updated to conform to the updated GHG protocol in Summer 2005.

These tools reflect many of the features of well-known and widely accepted protocols. In addition, they anticipate a number of questions that pulp and paper mills must address when preparing facility-level or company-level inventories. A special effort has been made to ensure that the tools are consistent with protocols issued by the Intergovernmental Panel on Climate Change (IPCC) and the WRI/WBCSD.

These tools estimate CO2 emissions from fossil fuel combustion based on the carbon content of the fuel (or a comparable emission factor) and the amounts burned. Carbon dioxide emissions from biomass combustion are not counted as greenhouse gas emissions, a convention common to most of the protocols examined in this review, but can be reported as "supporting information" as called for in the WRI/WBCSD GHG Protocol. Methane and nitrous oxide emissions from combustion processes, both fossil fuel and biomass, are estimated using emission factors. Methods are presented for estimating the fossil-CO2, methane and nitrous oxide emissions, from lime kilns and calciners. Greenhouse gas emissions from mill landfills and wastewater treatment plants are estimated using methods derived from those suggested by IPCC, as are emissions from vehicles and other fossil-fuel fired equipment. In all cases, however, companies may use site-specific information where it yields more accurate estimates of GHG emissions than the tools outlined in this report.

Using these tools, indirect emissions related to imports of electricity or steam and emissions attributable to exports of electricity or steam are included in the inventory results but tracked separately from direct emissions. The emissions from combined heat and power (CHP) plants are allocated using the WRI/WBCSD "efficiency method."

The calculation tools envision that companies will often construct inventory boundaries that include emissions from (a) all on-site "core" pulp and paper making operations, regardless of the ownership of the emission source, and (b) other company-owned sources included in widely accepted GHG inventory protocols (e.g. company-owned truck fleets). It is understood, however, that companies will select inventory boundaries suited to the objectives of the inventory.

To aid in interpreting the results of the inventory, these tools recommend that the inventory results include a list of the operations contained within the boundaries of the inventory and a list of emission factors used to estimate emissions. The format suggested for presenting the results of the inventory allows a company to separate the emissions that are "owned" by the company (direct emissions) from those that are not (indirect emissions). The company is free to select the method for determining the ownership of emissions, but the method must be explained in the inventory results. The user is directed to the WRI/WBCSD GHG Protocol for guidance on how to determine ownership of emissions from partly-owned or partly-controlled sources.