This is Tanaka speaking. I would like to thank our shareholders and investors for their continued support and advice on the business activities of the Einos Group. I will explain the financial results for the Q1 of fiscal 2020 based on the PowerPoint slides. Please refer to Slide 2. Operating income for the Q1 of fiscal 2020 was 21,000,000,000 yen down 28,300,000,000 yen year on year.
Excluding inventory valuation, operating income was 83,200,000,000 yen an increase of 14,200,000,000 yen year on year. Operating income declined largely due to the COVID-nineteen pandemic. And as noted at the bottom of the slide, the decline in crude oil prices, which led to a 62,200,000,000 yen inventory valuation loss in the energy business and a significant decline in profit in the oil and natural gas exploration and production business due to lower sales prices. In addition, sales volumes of petroleum products, including jet fuel, declined as a result of travel restriction, and the production was reduced at the Caseronas copper mine in Chile as a result of reduced manpower amid the pandemic. Despite negative factors related to COVID-nineteen, operating income excluding the inventory effect, as shown in the middle, was up year on year, driven by strong petroleum product margins in Japan, primarily due to the time lag, a larger sized deal in the real estate development subsidiary, Nippo, increased sales of electronic materials amid the teleworking trend and increased demand for telecommunications and a decrease in expenses due to the time lag and cost reduction activities.
Please refer to Slide 3. Our full year operating income for fiscal 2020 is projected at 165,000,000,000 yen excluding inventory valuation, unchanged from the previous forecast announced in May. In our previous announcement, we forecasted in we factored in the impact of COVID-nineteen on demand for petroleum and other products for the 1st 6 months, but not for the latter 6 months of the year. The Q1 results of JPY 83,200,000,000 represents 51% of the full year forecast, but this was largely due to a significant contribution of temporary factors such as a time lag in petroleum product margins. On the other hand, we do not expect to revise our full year forecast due to deteriorating factors, such as petrochemical margins, which are currently even weaker than in the April June quarter and lower sales volumes in the second half of the year due to the impact of the pandemic.
With regards to shareholder returns, we have not revised our basic policy outlined in our 2nd medium term management plan announced in May with a stable dividend of no less than 22 yen per share and a 3 year total return ratio of 50% or more of net income, excluding inventory valuation. Please refer to Slide 5 for the business environment. In April, the price of Dubai crude oil fell below $20 per barrel due to the impact of COVID-nineteen as well as the lack of agreement on production cut at the OPEC plus meeting held in March. Thereafter, the price rise again on the OPEC plus agreement on the extension of production cut, the lifting of the lockdown and the resumption of economic activity in many countries, and the price exceeded $40 per barrel. The copper price was at the $0.10 level per pound at the beginning of the year, but it rose sharply to 0.0 $2.90 per pound on expectations of recovery in copper demand following the resumption of economic activity in China as well as fears of reduced supply due to the spread of COVID-nineteen in copper ore producing countries.
Please refer to Page 6. The white oil product margins deteriorated significantly from March to April due to the decline in crude oil prices, but then turned back upward, mainly due to the time lag caused by the recovery in crude oil prices. Parazylene margins rose temporarily towards May as producers responded to production cut. But due to the lack of improvement in supply demand, the margins declined again and remained stagnant. Slide 8 provides details of P and L.
As I mentioned earlier, operating income for the Q1 of fiscal year 2020 was 21,000,000,000 yen down 28,300,000,000 yen from the same period last year. Excluding inventory valuation losses of 62,200,000,000 yen resulting from the decline in crude oil prices, operating income was JPY 83,200,000,000 Net income was JPY 3,500,000,000 a decrease of JPY 19,100,000,000 versus the same period last year. After adjusting for Nippo and other non controlling interest earnings, net income attributable to owners of the parent was negative 4,900,000,000 yen From Slide 9 onwards, I would like to explain the operating income and loss by segment. The following chart explains the details of our main businesses. Please look at the bottom of the page highlighted in gray.
The other segment increased by 11,700,000,000 yen to 19,500,000,000 yen This segment includes a gain on the sale of a large property in the Nippo Real Estate Development Business, which is one factor that contributed to an increase in earnings this quarter. Please refer to Slide 10. Excluding inventory valuation, the Energy business operating income was 43,800,000,000 yen an increase of 12,100,000,000 yen year on year. Petroleum products on the left improved 26,200,000,000 yen from the same period last year due to a steady increase in margins, mainly due to a time lag despite a decrease in sales volume due to the pandemic and the resulting lower refinery utilization rate. Petrochemicals is down 4,400,000,000 yen due to a decrease in sales volumes, mainly for presiding.
Electric power improved by 3,100,000,000 yen due to an increase in the number of contracts and sales volume, in line with the nationwide rollout of Eneno's Denki. Materials declined by 12,800,000,000 yen due to lower lubricant sales volume as auto manufacturers operations declined due to the impact of COVID-nineteen. Inventory adjustments by customers and lower needle coke sales volume as a result of lower electrode demand caused by weaker steel demand. Please refer to Slide 11. Operating income in the oil and gas exploration and production business declined year on year by 12,500,000,000 yen to 700,000,000 yen Sales volume increased by 21,000 barrels per day to 120,000 barrels per day, thanks to the contribution of the Mariner oilfield and the Killeen gasfield, which commenced our production in the middle of the previous year.
As a result, sales volume was positive 2,400,000,000 yen Expense and other was negative 4,400,000,000 yen Crude oil price deteriorated by 10,500,000,000 yen due to the decline in oil and gas prices. Slide 12, please. Operating income of the metals business increased by 2,900,000,000 yen to 19,200,000,000 yen Functional materials and thin film materials was up 3,400,000,000 yen due to increased sales driven by increased demands for data transmissions for telework and online learning. Mineral Resources saw a decrease in production volume by 4,000 tons to 36,000 tons due to the reduced manpower at the Casarones copper mine designed to prevent the spread of COVID-nineteen. On the other hand, copper prices rose from the beginning of the fiscal year to the end of June, resulting in a 3,100,000,000 yen improvement in earnings.
For smelting and recycling, while the sulfuric acid market deteriorated, high prices for precious metals were a positive factor, resulting in a generally similar level as in the same period of the previous year. Corporate expenses and others is down 4,400,000,000 yen due to the impact of internal transactions on consolidation. Page 13, please. I will start with the consolidated cash flow shown in the right. The 2 cash flow figures are shown.
I will explain the cash flow after the repayment of lease liabilities, shown by the dotted line, which is the basis for the 2nd medium term management plan. Operating cash flow was an inflow of 167,900,000,000 yen including operating income of 83,200,000,000 yen depreciation and amortization of 58,800,000,000 yen and a decrease in working capital due to lower resource prices of 25,900,000,000 yen Investing cash flow was an outflow of 82,000,000,000 yen as capital investments and loans were postponed due to the coronavirus pandemic, resulting in a free cash flow of 85,900,000,000 yen Subtracting JPY 41,500,000,000 in dividends and others, net cash flow was an inflow of JPY 44,400,000,000 The balance sheet is shown on the left hand side. Net interest bearing debt, excluding cash at hand, decreased by 48,500,000,000 yen to 1,850,300,000,000 yen mainly due to the 44,400,000,000 yen in net cash inflow. As a result, net DE ratio was 0.7x and equity ratio 29.1% as of the end of June 2020. Slide 14, please.
I would like to take you through main topics from April to date. As I explained earlier, on the cash flow slide, we assessed the impact of COVID-nineteen and minimized the number of cash based investments during the recent period. On the other hand, we steadily proceeded with the development of growth businesses in line with the long term vision and the second medium term management plan. In energy business, in July, we concluded an agreement with Shizuoka Prefecture on the establishment of a next generation energy supply platform to realize the next generation energy supply for and by the local community as well as various community services. We began collaboration, alliance and investment together with non industry players with the aim of improving the efficiency of core businesses, expanding renewable energy businesses and creating innovative businesses.
In May, the group commenced commercial operation of the Muroran Biomass Power Plant as an environmentally friendly renewable energy source. In the metals business, we have increased our capacity for electronic materials to meet the growing need for advanced materials in line with the advancement of IoT and AI. We believe that the scenario in 2,040, which we have outlined in our long term vision, will not change even in the face of the COVID-nineteen outbreak. We will continue to accelerate structural reforms and steadily develop and strengthen our growth businesses as we work towards the realization of the long term vision. The rest of slides are just for your information.
Slide 16 shows the key assumptions and Slide 17 shows details of sensitivity analysis. This concludes my presentation. Thank you very much for your kind attention.