Hidden flows

Hidden flows are resources associated with material extraction, and in this study, are excluded from the resource flow analysis as they do not enter the economy. An example of a hidden flow would be the large quantities of materials disturbed when extracting quarried materials. Hidden flows have been identified and quantified here as they have environmental impacts associated with them, and may be important when considering resource management in the South West.

Table 12 lists the quantified hidden flows associated with particular materials in the South West, as well as the proportion of hidden flows linked with materials and products exported. Although most of the coefficients used in calculating hidden flows were from the mining and quarrying industry, agricultural waste such as silage effluent or slurry, proved to be a significant flow (14.4 million tonnes). Silage effluent and slurry waste was removed from agricultural waste and included as a hidden flow because of its volume in comparison to other agricultural waste (see Table 13).

Table 12
Hidden flows associated with resources produced in the South West, in 2001
Hidden flow description Tonnes ('000s) Hidden flows associated with
products exported (%)*
Total hidden flows 37,539  
of which…  
Sugar beet leaves 20 0%
Straw input 1,176 5%
Agricultural waste*** 14,413 **
Logging residues 177 5%
Dead discards of fish (marine) 834 **
Drilling wastes from crude oil extractions 182 35%
Natural gas extraction 196 11%
Peat extraction 51 3%
Unused extractions from metal ore extraction <1 0%
Unused extractions from other mining activities 15,510 29%
Excavating & dredging 4,980 5%
* Hidden flows associated with products exported also includes estimates of hidden flows associated with products likely to have been imported into the South West, and then exported.
** No data available.
*** Agricultural waste includes silage effluent, farmyard manure and slurry.
Note: Totals may differ due to rounding.
Source: BGS, 2002; Bringezu & Shutz, 2001 & 2001a, Highley et al., 2003 and University of Plymouth, 2003

As mining and quarrying is an important sector in the South West, a more detailed assessment of the hidden flows associated with the sector was carried out. Figure 5 compares the actual resource extracted with its associated hidden flows.

Figure 5
A comparison between materials mined and quarried in the South West, with their associated hidden flows, in 2001


Note : Due to the large scale of limestone and dolomite mining in the South West (23.2 million tonnes) and associated hidden flows (10.3 million tonnes), it was not included in this figure. Similarly, metal ores were small (0.04 million tonnes) in comparison, and as a result not presented.

Sources: BGS, 2002; Bringezu & Shutz, 2001 & 2001a, Highley et al., 2003 and University of Plymouth, 2003