Docs / What we have found

Flows that are not substances at all

Part of What we have found, the class where the row has no substance identity to get wrong: a laboratory measurement, a burden that is not matter, a place in a state.

Measurements over many molecules

Fourteen kinds of flow in these lists are laboratory quantities rather than substances — 180 flows in EF 3.1, 40 in ecoinvent 3.12, 45 in 3.8 and 41 in BAFU. Chemical oxygen demand is the mass of oxygen a chemical oxidant consumes in breaking down everything oxidisable in a sample — the oxygen is not in the discharge at all; it is what the laboratory's reagent gave up. Biochemical oxygen demand is the same quantity measured by letting bacteria do the oxidising over five days, and BOD5 and BOD20 are different numbers, so the five days are part of the definition. Total organic carbon is one element counted across an unstated set of molecules. Nitrogen, organic bound — which all three lists give dinitrogen's registry number — is the same kind of thing.

Rows with no substance identity to get wrong

Chemical oxygen demand is the plainest member of a class that runs through every list here. These rows are not errors in a substance's identity; they are flows that have no substance identity to get wrong, sitting in a list built to hold substances. Read as chemistry, they produce nonsense — and every automated step that enriches a flow from its registry number will try.

Burdens that are not matter

BAFU carries six noise rows — aircraft, lorry, passenger car, freight and passenger rail — counted per person-kilometre for passengers and per tonne-kilometre for freight. What is counted is not how much noise there is but how much transport it accompanied. Noise has no formula, no mass and no registry number, and no chemical ontology has a class for it (#387).

Land classes

ecoinvent ships 182 land flows, BAFU 152 and Stepwise 2006 41, named Occupation, arable, conservation tillage or Transformation, from forest, primary. These are not substances but places in a state, measured in m² and m²·a; they need fields a substance record has no room for — what the land is, what it was, and what it became — which is why they are given their own kind of record rather than a chemical one (#382).

What the land was is the field the record still does not have. Thirteen of Stepwise's 41 rows are about it: Occupation, sealed, on grassland is a paved square metre that used to be grassland, and Stepwise charges 0.7 for it where the same paving on arable land costs 0.2 — so the previous state is what the number turns on, and every axis this project has describes the land as it is. Those thirteen are published under Stepwise's own names, and listed as unreadable in tests/data/observed-land-classes.json rather than left silent (#810). Whether the axes should gain a previous state is #818.

One quantity in two directions

Waste heat is shipped as an emission by every list — EF 12 flows, ecoinvent 13, BAFU 14 — and BAFU also ships Energy, waste heat, air as a resource taken from the air. The same physical quantity is both a release and an intake depending on which row you read (#402).

The decision, in every case

These rows are kept and published, with a record type that fits what they are, and they are kept out of the chemical enrichment that would otherwise attach a structure, a formula and a set of trade names to a laboratory procedure. The registry number is removed where a list supplied one, because there is nothing to correct it to.