Petrochemical mass balance methodology

The category at business/processes/production/petrochemical/massbalance provides a methodology for calculating greenhouse gas emissions associated with the production of petrochemicals. The methodology is based on a mass-balance approach which accounts for all of the carbon contained within process feedstocks, products and by-products. This methodology represents the Tier 2 approach described by the IPCC Guidelines for National Greenhouse Gas Inventories (NGGIP).

To use this category, specify the type of petrochemical production using the product drill choice.

Next, specify the quantity of feedstock and petrochemical product using the primaryFeedstockMass and productMass profile item values. The returned value represents CO₂ emissions based on these quantities, using default information regarding the type of feedstock used and the carbon contents of both the feedstock and product. The default type of feedstock follows IPCC guidelines and is represented by the primaryFeedstock data item value. The calculation assumes that all feedstock carbon unaccounted for in the process products is emitted as CO₂.

Users can override the default carbon content value for both feedstock and product by using the primaryFeedstockCarbon and productCarbon profile item values.

Specifying multiple feedstocks and products

Users can additionally specify up to three feedstock types as well as three process by-products. In each case, the calculation uses the repsective quantities and carbon contents in the balance of carbon entering and leaving the manufacture process. To specify the quantities of each feedstock set the appropriate values using the following profile item values:

• secondaryFeedstockMass and secondaryFeedstockCarbon
• tertiaryFeedstockMass and tertiaryFeedstockCarbon
• primaryByProductMass and primaryByProductCarbon
• secondaryByProductMass and secondaryByProductCarbon
• tertiaryByProductMass and tertiaryByProductCarbon

Using default carbon contents

If the carbon contents of the feedstocks or by-products are not known, users can use default values which follow the IPCC guidelines. In this case, users can omit the associated carbon-related profile item values (but must still specify the mass-related values) and must instead specify the name of the feedstock/by-product using the appropriate profile item value:

• secondaryFeedstock
• tertiaryFeedstock
• primaryByProduct
• secondaryByProduct
• tertiaryByProduct

The value specified must match one of the drill options in the subcategory /business/processes/production/petrochemical/massbalance/carboncontent, from which the appropriate value for carbon content is looked up. This category lists a number of petrochemical products and feedstocks as well as oil- and petroleum-derived fuels which are used as feedstocks in the petrochemical industry.

Note: IPCC suggests two default feedstock types for ethylene production - ethane (for North America, South America and Australia) and and naphtha (all other continents). Ethane is used by default, but users can override this and specify naphtha - or another feedstock - if appropriate.