DEPUIS: Reference data on the Web: Lifecycle assessment ontology


Reference data on the Web	DEPUIS

Cover page
1 Introduction
2 Simple examples of reference data
3 Simple application using reference data

4 Lifecycle assessment for an individual house
A Lifecycle assessment ontology
B URI assigned to a thing by an ISO standard

A Lifecycle assessment ontology

A.1 Introduction

LCA is about activities which are supplies of material, energy, or transportation.

The LCA calculations are made using supplies to the place of use. Such a supply activity can be split into two activities:

supply to a depot;
transport from a supply depot to the place of use.

This split allows transport costs to remote sites to be included.

For an activity, the LCA information consists of:

flows from resources, such as coal from the ground; or
flows to the environment, such as CO₂ to the atmosphere.

This is shown in Figure 1.

Figure 1: Elementary flows

There are two approximations implicit in the approach, as follows:

It is assumed that everything scales, so that the supply of 2 tonnes of carbon steel rebar from a depot in Norway would result in the emission of 2 × 30 tonnes of CO₂ (scaling from Figure 1).

This is a reasonable assumption, given that we are considering Δs.
It is assumed that the supplies are independent, so that the flows from resources and to the environment for the supply of 1 tonne of rebar and 1 tonne or plasterboard are equal to the sum of the flows for suppling each independently.

This is not true, because gypsum for plasterboard is a by-product of the generation of electricity using coal, and electricity is required to make rebar.

NOTE The interactions may be taken into account in the data in some way. For example it may be assumed that an increased requirement for gypsum is always accompanied by an increased requirement for coal generated electricity. It would be interesting to speak to an expert about this - DL.

Whatever assumptions are included in the raw flow figures, the simple addition of flows associated with different supplies is a useful first estimate.

A.2 LCA activities

For each iso15926:physical_object used, there is a corresponding activity that supplies it to the place of use. The LCA information is about classes of supply activity.

The classes of activity exist in a hierarchy, such as that shown below:

activity
  transport
    transport material

  supply material from depot
    supply steel from stockholder

      supply carbon steel rebar from stockholder
        supply deformed carbon steel rebar from stockholder

          supply deformed carbon steel rebar from stockholder in Europe
            supply deformed carbon steel rebar from stockholder in Norway

            supply 20 mm deformed carbon steel rebar to BS 4449 grade 460B from stockholder in Europe

The class of activity that corresponds to a particular supply may be the intersection of:

supply 20 mm deformed carbon steel rebar to BS 4449 grade 460B from stockholder in Europe;
supply deformed carbon steel rebar from stockholder in Norway.

For a generic class, such as "supply material from depot", it is not possible to give LCA information, because there is too much variability between different members of the class.

For a specific class, such as "supply 20 mm deformed carbon steel rebar to BS 4449 grade 460B from stockholder in Europe", there may be no LCA information available because nobody has calculated it.

LCA information is likely to be available for an intermediate class, such as "supply deformed carbon steel rebar from stockholder in Europe". A key task of LCA software is to find an appropriate class for which LCA information is available.

A.3 Normalisation of LCA data

The LCA information is recorded for a class of activity as follows:

a subclass is defined with a reference magnitude, such as the supply of 1 kg or 1 tonne;
the inputs from resources and outputs to the environment for this subclass are recorded;
there is an assumption that the magnitudes of the inputs and outputs can be scaled for subclasses with different magnitudes.

It may be possible to record this formally using the existing capabilities of ISO 15926-2 or OWL, but a way of doing so has not yet been documented. A next best alternative may be to define the class of activity that is:

the supply of 1 tonne of deformed carbon steel rebar from stockholder in Europe,

and to record that this is a subclass of the class of activity that is:

all activities with an aggregate supply of 2 tonnes of CO₂ to the atmosphere.

The OWL representation of this is as follows:

:supply_deformed_carbon_steel_rebar_from_stockholder_in_Europe
  =
   [ owl:intersectionOf
      ( depuis:SupplyOfMaterialWithLcaBatteryLimits ;
        [ owl:onProperty depuis:materialSupplied ;
          owl:allValuesFrom lcaInfo:deformed_carbon_steel_rebar
        ]
        [ owl:onProperty depuis:receiving_activity ;
          owl:allValuesFrom lcaInfo:steel_stockholding_in_Europe
        ]
      )
   ] .

[ owl:intersectionOf
   ( :supply_deformed_carbon_steel_rebar_from_stockholder_in_Europe
      [ owl:onProperty depuis:materialSupplied ;
        owl:allValuesFrom
         [ owl:onProperty depuis:hasMass ;
           owl:hasValue [ depuis:tonne_scale [ depuis:decimal "1" ]
         ]
      ]
   )
]
  rdfs:subClassOf
   [ owl:onProperty depuis:hasAggregateOutput ;
     owl:allValuesFrom
      [ owl:intersectionOf
         ( [ owl:onProperty  depuis:aggregationClassOfMaterial ;
             owl:hasValue  lcaInfo:CarbonDioxide
           ]
           [ owl:onProperty  depuis:aggregationReceivingActivity ;
             owl:hasValue  lcaInfo:Atmosphere
           ]
           [ owl:onProperty  depuis:materialSupplied ;
             owl:allValuesFrom
              [ owl:onProperty  depuis:hasMass ;
                owl:hasValue  [ depuis:tonne_scale [ depuis:decimal "2.0" ]
              ]
           ]
         )
      ]
   ] .

Using this information, it is necessary to deduce from, the OWL:

:my_supply_of_deformed_carbon_steel_rebar
  a  :supply_deformed_carbon_steel_rebar_from_stockholder_in_Europe ;
  depuis:materialSupplied
    [ depuis:hasMass [ depuis:tonne_scale [ depuis:decimal "2" ] ] ] .

:my_supply_of_deformed_carbon_steel_rebar
  depuis:hasAggregateOutput
    [ depuis:aggregationClassOfMaterial  lcaInfo:CarbonDioxide ;
      depuis:aggregationReceivingActivity  lcaInfo:Atmosphere ;
      depuis:materialSupplied
        [ depuis:hasMass [ depuis:tonne_scale [ depuis:decimal "4.0" ] ] ]
    ] .

This inferencing is currently outside the scope of OWL, and will have to be supplied by the LCA software.

A.4 Ontology for LCA data

A.4.1 SupplyOfMaterial

An object is a depuis:SupplyOfMaterial if and only if:

it is an iso15926:activity;
it supplies an intended iso15926:physical_object to an intended receiving activity.

OWL specification:

-->
<owl:Class rdf:about="&depuis;SupplyOfMaterial">
 <rdfs:subClassOf rdf:resource="&iso15926;activity"/>
</owl:Class>
<!--

A.4.2 SupplyOfMaterialWithLcaBatteryLimits

An object is a depuis:SupplyOfMaterialWithLcaBatteryLimits if and only if:

it is a depuis:SupplyOfMaterial;
the battery limits are such that each input is from a lca:resource and each output, except the intended iso15926:physical_object, is to an lca:environment.

NOTE In the CASCADE project, it was realised that it is convenient to regard LCA information as flows between activities. Hence:

material is supplied to an activity which stores it or uses it;
the "technosphere" is an activity;
the "atmosphere" is an activity.

In ISO 15926 and other top ontologies, the distinction between activities and other physical things is usually vague. Something is often regarded as an activity if it is necessary to record:

the flows in an out;
the cost.

OWL specification:

-->
<owl:Class rdf:about="&depuis;SupplyOfMaterialWithLcaBatteryLimits">
 <rdfs:subClassOf rdf:resource="&depuis;SupplyOfMaterial"/>
</owl:Class>
<!--

A.4.3 TransportOfMaterial

An object is a depuis:TransportOfMaterial if and only if:

it is a depuis:SupplyOfMaterial;
the supply is achieved by taking the intended iso15926:physical_object from somewhere else, and delivering it substantially unaltered.

OWL specification:

-->
<owl:Class rdf:about="&depuis;TransportOfMaterial">
 <rdfs:subClassOf rdf:resource="&depuis;SupplyOfMaterial"/>
</owl:Class>
<!--

A.4.4 TransportOfMaterialWithLcaBatteryLimits

An object is a depuis:TransportOfMaterialWithLcaBatteryLimits if and only if:

it is a depuis:TransportOfMaterial;
the battery limits are such that each input, except the transported iso15926:physical_object, is from a lca:resource and each output, except the transported iso15926:physical_object, is to an lca:environment.

NOTE An activity that is an assembly of a depuis:SupplyOfMaterialWithLcaBatteryLimits and a depuis:TransportOfMaterialWithLcaBatteryLimits is itself a depuis:SupplyOfMaterialWithLcaBatteryLimits.

OWL specification:

-->
<owl:Class rdf:about="&depuis;TransportOfMaterialWithLcaBatteryLimits">
 <rdfs:subClassOf rdf:resource="&depuis;TransportOfMaterial"/>
</owl:Class>
<!--

A.4.5 material_supplied

An object is a depuis:materialSupplied if and only if:

it is a basics:function from depuis:SupplyOfMaterial to iso15926:physical_object;
it gives the iso15926:physical_object supplied by a depuis:SupplyOfMaterial.

NOTE It is convenient to regard this relationship as being between a depuis:SupplyOfMaterial and a temporal part which continues to exist after the activity.

If the depuis:SupplyOfMaterial is a depuis:TransportOfMaterial then it is convenient to regard this relationship as being with a temporal part which existed both before and after the activity.

OWL specification:

-->
<owl:FunctionalProperty rdf:about="&depuis;material_supplied">
 <rdfs:domain rdf:resource="&depuis;SupplyOfMaterial"/>
 <rdfs:range rdf:resource="&iso15926;physical_object"/>
</owl:FunctionalProperty>
<!--

A.4.6 receiving_activity

An object is a depuis:receiving_activity if and only if:

it is a basics:function from depuis:SupplyOfMaterial to iso15926:activity;
it gives the iso15926:activity to which a depuis:SupplyOfMaterial makes the supply.

OWL specification:

-->
<owl:FunctionalProperty rdf:about="&depuis;receiving_activity">
 <rdfs:domain rdf:resource="&depuis;SupplyOfMaterial"/>
 <rdfs:range rdf:resource="&iso15926;activity"/>
</owl:FunctionalProperty>
<!--

A.4.7 sourceOfMaterial

An object is a depuis:sourceOfMaterial if and only if:

it is a basics:function from depuis:TransportOfMaterial to iso15926:activity;
it gives the iso15926:activity at which a depuis:TransportOfMaterial makes a pickup.

OWL specification:

-->
<owl:FunctionalProperty rdf:about="&depuis;sourceOfMaterial">
 <rdfs:domain rdf:resource="&depuis;TransportOfMaterial"/>
 <rdfs:range rdf:resource="&iso15926;activity"/>
</owl:FunctionalProperty>
<!--

A.4.8 AggregateSupplyOfMaterial

An object is an depuis:AggregateSupplyOfMaterial if and only if:

it is a depuis:SupplyOfMaterial;
it is an aggregation of supplies of material that are:
- of a class specified by an depuis:aggregationClassOfMaterial; and
- to an activity specified by an depuis:aggregationReceivingActivity, or any part of that activity.

OWL specification:

-->
<owl:Class rdf:about="&depuis;AggregateSupplyOfMaterial">
 <rdfs:subClassOf rdf:resource="&depuis;SupplyOfMaterial"/>
</owl:Class>
<!--

A.4.9 hasAggregateOutput

An object is a depuis:hasAggregateOutput if and only if:

it is a basics:mapping from iso15926:activity to depuis:AggregateSupplyOfMaterial;
it gives an depuis:AggregateSupplyOfMaterial for the iso15926:activity.

OWL specification:

-->
<owl:ObjectProperty rdf:about="&depuis;hasAggregateOutput">
 <rdfs:domain rdf:resource="&iso15926;activity"/>
 <rdfs:range rdf:resource="&depuis;AggregateSupplyOfMaterial"/>
</owl:ObjectProperty>
<!--

A.4.10 aggregationClassOfMaterial

An object is a depuis:aggregationClassOfMaterial if and only if:

it is a basics:function from depuis:AggregateSupplyOfMaterial to iso15926:class_of_individual;
it gives the iso15926:class_of_individual for which a depuis:AggregateSupplyOfMaterial is aggregated.

OWL specification:

-->
<owl:FunctionalProperty rdf:about="&depuis;aggregationClassOfMaterial">
 <rdfs:domain rdf:resource="&depuis;AggregateSupplyOfMaterial"/>
 <rdfs:range rdf:resource="&iso15926;class_of_individual"/>
</owl:FunctionalProperty>
<!--

A.4.11 aggregationReceivingActivity

An object is a depuis:aggregationReceivingActivity if and only if:

it is a basics:function from depuis:AggregateSupplyOfMaterial to iso15926:activity;
it gives the iso15926:activity for which a depuis:AggregateSupplyOfMaterial is aggregated.

A supply to any part of the iso15926:activity is included in the aggregation.

OWL specification:

-->
<owl:FunctionalProperty rdf:about="&depuis;aggregationReceivingActivity">
 <rdfs:domain rdf:resource="&depuis;AggregateSupplyOfMaterial"/>
 <rdfs:range rdf:resource="&iso15926;activity"/>
</owl:FunctionalProperty>
<!--

A.5 EU LCA Info hub

The EU LCA "Info hub" http://lca.jrc.ec.europa.eu/ contains LCA data for "steel rebar". A download from the database contain the data as an XML file.

The XML file has been transformed by XSLT to an HTML file, which is accessible as: http://lca.jrc.ec.europa.eu/lcainfohub/datasets/html/processes/Steel_rebar_Eurofer_268a11fb-baf2-4b9e-8867-38bea0e76ef6_01.00.001.html.

To shown the approach, an extract from the full XML file for steel rebar has been created, which contains just:

a description of the production process;
the reference amount of steel rebar;
the amount of CO₂ emitted.

All the other emissions, the modelling and validation information, and the administrative information has been removed from this file.

NOTE Within the LCA Info Hub the supply of steel rebar has the identifier "268a11fb-baf2-4b9e-8867-38bea0e76ef6". However, it is not straightforward to use this identifier to navigate either to the XML file of data about the supply of steel rebar or to the HTML presentation of it.

For life sciences, a Web-friendly approach has been developed in which each object of interest is assigned a URN, and a Web resolution service is provided to supply information about it. This approach is described in http://lsid.biopathways.org/resolver/.

A more Web friendly approach would be to:

assign to the steel rebar supply process a URN, such as urn:lca:lcainfohub:process:steel_rebar;
provide a resolver (analogous to the LSID resolver) http://lca.jrc.ec.europa.eu/lcainfohub/resolver/;
assign to the HTML presentation of information about the steel rebar supply process the HTTP URI http://lca.jrc.ec.europa.eu/lcainfohub/resolver/urn:lca:lcainfohub:process:steel_rebar.

The information about the steel rebar supply process can be recorded using the Depuis LCA ontology, as follows:

:urn:lca:lcainfohub:process:steel_rebar
  =
   [ owl:intersectionOf
      ( depuis:SupplyOfMaterialWithLcaBatteryLimits ;
        [ owl:onProperty depuis:materialSupplied ;
          owl:allValuesFrom lcaInfo:steel_rebar
        ]
      )
   ] .

[ owl:intersectionOf
   ( :urn:lca:lcainfohub:process:steel_rebar
      [ owl:onProperty depuis:materialSupplied ;
        owl:allValuesFrom
         [ owl:onProperty depuis:hasMass ;
           owl:hasValue [ depuis:kilogramScale [ depuis:decimal "1" ]
         ]
      ]
   )
]
  rdfs:subClassOf
   [ owl:onProperty depuis:hasAggregateOutput ;
     owl:allValuesFrom
      [ owl:intersectionOf
         ( [ owl:onProperty  depuis:aggregationClassOfMaterial ;
             owl:hasValue  lcaInfo:CarbonDioxide
           ]
           [ owl:onProperty  depuis:aggregationReceivingActivity ;
             owl:hasValue  lcaInfo:Atmosphere
           ]
           [ owl:onProperty  depuis:materialSupplied ;
             owl:allValuesFrom
              [ owl:onProperty  depuis:hasMass ;
                owl:hasValue  [ depuis:kilogramScale [ depuis:decimal "1.001878674" ]
              ]
           ]
         )
      ]
   ] .

Discussion of the objects within the "lcaInfo" namespace in the examples above - still to do!!!!