True Cost of Waste
What does The true Cost of Waste Calculator do?
Government policy, public opinion and good business practice are all driving a reduction in resource use and carbon emissions from businesses. This tool aims to equip construction companies with carbon accounting and attributing costs for materials wasted on construction, sites. As well as measuring the carbon impacts associated with the wasted construction products, the calculator also takes into consideration the overall cost associated with material wastage of a particular product.
The tool calculates the carbon impact of wasted construction materials using embodied carbon data from Life Cycle Analysis (LCA) for the materials listed. LCA is an objective process to evaluate the environmental burdens associated with a product, process or activity by identifying energy and materials used emissions and wastes released to the environment.
The cost of wasted materials is calculated using price information from Laxton's Building Price Book 2007, a standard quantity surveying book used by the construction industry. The calculator includes the labour costs paid for filling up a skip with the wasted materials generated on site and the price paid to remove the full skip from the site and whether it is segregated onsite or sent off as mixed waste.
Default wastage rates are set for each material which have been taken from BRE's Green Guide to Specification; alternative wastage rates can be set to show the effect on both embodied carbon and cost. The tool can be used at both the forecasting stage for waste i.e. to help set targets and for actual waste measurements.
What data needs to be entered?
A company needs to register to use the calculator. Projects then need to be registered. Users have to be set up with a username and a password so they can access the calculator.
The type and quantity of materials that are to be used on a construction site should be entered. Default wastage rates are set against products assigned to 11 material groups as a percentage. The user can also add in their own wastage rates. The wastage rates can be used to predict how much material waste will be generated by a project overall.
For example: ‘ceramics and tiles' are listed on the calculator. Under this group, construction products manufactured using ceramic materials are listed. This includes ‘internal building tiles'.
To quantify the amount of ‘internal building tiles' waste predicted on the project, the total quantity of ‘internal building tiles' likely to be required needs to be entered. The calculator will assign default wastage rate figures for that particular material to this figure. Users can then enter up to two scenarios based on different wastage rates.
For example: A housing development project expects to require 1000m2 of internal building tiles to cover the bathroom walls and floors. The default wastage rate for these tiles is 8%. Therefore 80m2 of the internal building tiles is predicted to be wasted throughout the project using the default value. The user can enter up to two wastage rates for each product; therefore if the ‘internal; roof tiles' has a predicted wastage rate of 5%; then the predicted wastage will be 50m2.
The calculator will then automatically determine the carbon emissions associated to the amount of material that is to be wasted. So for the predicted 80m2 of internal building tiles waste, the carbon cost is 0.7 tonnes, the material cost is £1,395 and the true cost of that waste is £1,425 (this is the material, labour and disposal cost) . If the waste is segregated on site, then the true cost of waste decreases slightly to £1,415.
Data Sources
The information used in the True Cost of Waste Calculator is based on the following sources.
- The default wastage rates of materials are based on wastage rates listed in the BRE's Green Guide to Specification; www.thegreenguide.org.uk/
- Carbon data - All details have been extracted from Simapro - Approved processes V1.7; the only data source that has been used is Ecoinvent; For a significant number of the categories averages over a range of inventory data sets have been used; For completeness the GWP details are a summation of the Cradle to gate data and disposal related data. This is necessary to reduce the disproportionate effect of the "negative" impact of wood related products
- Material cost data and the labour cost was established from Laxton's Price Book 2008
- Skip cost information was based on a telephone survey of 11 waste management companies who provide skip hire and waste removal services for construction waste; undertaken on the 23rd of July '08.
