252
As metal stocks in a society are important sources of secondary resources,
research related to the assessment of stocks has been increasing (Gerst and Graedel
2008 ). Using satellite night-time light observation data is an innovative and interesting methodological approach to stock estimation (Takahashi et al. 2009 ; Hsu et al.
2013 ). On the conceptual aspect of stocks as resources, classifi cation of secondary
resources in the anthroposphere was proposed (Hashimoto et al. 2008 ), based on the
classifi cation of primary resources in the lithosphere, i.e. so-called McKelvey diagram (McKelvey 1972 ). Analysis of stocks must be an important topic in coming
decades.
2.5 Phosphorus in Waste
Phosphorus is as an essential nutrient for agriculture, but phosphate rock is a nonrenewable resource and its deposits will be exhausted in a long term. Therefore, in
addition to increasing phosphorus use effi ciency in agricultural systems, phosphorus needs to be recovered from all current waste streams (Cordell et al. 2011 ).
Especially, wastes rich in phosphorus can represent new sources. MFA can provide
an effective tool to identify such new sources.
Sewage sludge is one candidate as a potential source of phosphorus and commonly utilized by spreading directly to farm land (Lederer and Rechberger 2010 ).
However, by conducting MFA of phosphorous in Gothenburg, Sweden, Kalmykova
et al. ( 2012 ) concluded that solid waste incineration residues represented a large
underestimated sink of phosphorus and that focusing on wastewater as the sole
source of recovered phosphorus was not suffi cient. Further, Matsubae-Yokoyama
et al. ( 2009 ) analyzed availability of phosphorus resources that remain untapped for
Japan and found that the quantity of phosphorus in iron and steel-making slag was
almost equivalent to that in imported phosphate ore in terms of both amount and
concentration.
2.6 Waste Plastics
Attention has been paid to the management of waste plastics. MFAs have been carried out for different types of plastics in many countries, e.g. plastics streams in
general in Austria and Poland (Bogucka et al. 2008 ), in Germany (Patel et al. 1998 ),
in India (Mutha et al. 2006 ), in the Netherlands (Joosten et al. 2000 ) and in Serbia
(Vujic et al. 2010 ); for polyethylene terephthalate fl ows in Colombia (Rochat et al.
2013 ) and in the US (Kuczenski and Geyer 2010 ); fl ows of polyvinyl chloride in
Y. Moriguchi and S. Hashimoto
As metal stocks in a society are important sources of secondary resources,
research related to the assessment of stocks has been increasing (Gerst and Graedel
2008 ). Using satellite night-time light observation data is an innovative and interesting methodological approach to stock estimation (Takahashi et al. 2009 ; Hsu et al.
2013 ). On the conceptual aspect of stocks as resources, classifi cation of secondary
resources in the anthroposphere was proposed (Hashimoto et al. 2008 ), based on the
classifi cation of primary resources in the lithosphere, i.e. so-called McKelvey diagram (McKelvey 1972 ). Analysis of stocks must be an important topic in coming
decades.
2.5 Phosphorus in Waste
Phosphorus is as an essential nutrient for agriculture, but phosphate rock is a nonrenewable resource and its deposits will be exhausted in a long term. Therefore, in
addition to increasing phosphorus use effi ciency in agricultural systems, phosphorus needs to be recovered from all current waste streams (Cordell et al. 2011 ).
Especially, wastes rich in phosphorus can represent new sources. MFA can provide
an effective tool to identify such new sources.
Sewage sludge is one candidate as a potential source of phosphorus and commonly utilized by spreading directly to farm land (Lederer and Rechberger 2010 ).
However, by conducting MFA of phosphorous in Gothenburg, Sweden, Kalmykova
et al. ( 2012 ) concluded that solid waste incineration residues represented a large
underestimated sink of phosphorus and that focusing on wastewater as the sole
source of recovered phosphorus was not suffi cient. Further, Matsubae-Yokoyama
et al. ( 2009 ) analyzed availability of phosphorus resources that remain untapped for
Japan and found that the quantity of phosphorus in iron and steel-making slag was
almost equivalent to that in imported phosphate ore in terms of both amount and
concentration.
2.6 Waste Plastics
Attention has been paid to the management of waste plastics. MFAs have been carried out for different types of plastics in many countries, e.g. plastics streams in
general in Austria and Poland (Bogucka et al. 2008 ), in Germany (Patel et al. 1998 ),
in India (Mutha et al. 2006 ), in the Netherlands (Joosten et al. 2000 ) and in Serbia
(Vujic et al. 2010 ); for polyethylene terephthalate fl ows in Colombia (Rochat et al.
2013 ) and in the US (Kuczenski and Geyer 2010 ); fl ows of polyvinyl chloride in
Y. Moriguchi and S. Hashimoto