3.2.4. The Factory Passive System Level

In the factory passive system (Figure 5d), the steel mining industry was still the sector with the largest carbon emissions and increment (CO2 emissions increased by 851 Mt). This was related to the over-capacity inertia of the steel industry in China, and it was difficult to achieve de-capacity in short term which was also pointed out by Zhou and Yang [33]. Results also show that the non-ferrous metal mining industry and chemical industry had become new driving forces of carbon emission growth (the relative growth rate of non-ferrous metal industry reached 171%, accounting for an increase of 2.9% in the emission structure, and the chemical industry's emission growth rate reached 1.01, accounting for an increase of 2.0% in the emission structure). The improvement of macroeconomics, industrialization and urbanization had brought huge demand for non-ferrous metal materials and chemical raw materials, and also provided a good economic environment for relevant manufacturing. The significant profit growth of chemical industry (in 2015, its profit increased by 7.7%, which is the largest increase in all industrial sectors of China [34]) brought great opportunities for the development of chemical-related enterprises.

Compared with previous work in this field, Li et al. [11] conclude that in 2013 the 'electricity and heating' emitted the most in the secondary industry (factory), following by 'metals' (including ferrous and non-ferrous), while chemical industry just accounted for nearly 3.1%. This differs from our results, as the division of stages of carbon flow diagram in their work only included energy sources and end use sectors, and the 'electricity and heating' was regarded in a parallel relation with other industrial sectors. But in fact, most of electricity and heating served as secondary energy supply and were consumed by steel, non-ferrous metal and chemical industries. When we discuss carbon emissions responsibility, it is inappropriate to allocate all of these emissions to the electricity generation sector. Concerning this, in another work, Li et al. [35] allocated the emission responsibility of electricity generation to end use sectors and kept in line with our result that the ferrous (steel) industry took the largest CO2 emissions responsibility, but the main difference was that the non-ferrous metal industry only accounted for 3% of end use sectors responsibility in their study. This was because in their carbon flow Sankey diagram, a large amount of emissions caused by energy loss in the conversion stage such as electricity and heat generation were regarded as conversion loss and not allocated to end use responsibility. However, the

fact is that the non-ferrous industry consumed a lot more electricity and heat but less direct fuels than other industries [25]. Since the emissions responsibility of electricity generation had been allocated to end use sectors, the loss of this stage should also be considered. This just illustrates the importance of energy allocation analysis method in carbon emissions analysis.

We also found that the industry whose growth of carbon emissions slowed significantly was the non-metallic mineral mining manufacturing industry. Although it had large emissions (517 Mt CO2 in 2005), the relative growth rate was only 60%, and the occupation ratio of emissions shrunk by 2.0%. This partly differs from previous work [11] concluding that the non-metallic mineral would continue to increase rapidly. Actually, during the "12th Five-Year Plan" period when China had strengthened the management and rectification of non-metallic mineral mines, standardized the mining order, and shut down nearly 10,000 nonstandard enterprises [36]. The result illustrates the effectiveness of comprehensively considering TRO index to analyze the changing trend.
