An innovative development by a team of Tel Aviv University (TAU) researchers allows for the conversion of the wet raw waste that we throw in the trash into liquid and solid biofuels, without the need to dry the waste. The researchers assess that fuels produced from organic waste can meet about a third of Israel’s marine fuel consumption.

The study was led by Professor Alexander Golberg of TAU’s Porter School of the Environment and Earth Sciences and was published in October 2023 in the journal Energy Conversion and Management: X. The research was conducted by PhD candidate Maya Mosseri in collaboration with engineer Michael Epstein, Professor Michael Gozin of the School of Chemistry at TAU’s Raymond and Beverly Sackler Faculty of Exact Sciences, and Professor Avraham Kribus of TAU’s Iby and Aladar Fleischman Faculty of Engineering.

Israel’s waste problem is escalating. In 2019, the country generated approximately 5.8 million tons of municipal waste, averaging about 1.76 kg (almost four pounds) of waste per person per day — about 30 percent more than the European average. This figure increases every year by about 2.6 percent. Currently, about 80 percent of household waste in Israel ends up in landfills.

Organic waste presents a significant challenge, harming the environment through greenhouse gas emissions, leachate formation, and the pollution of air, water, and soil, often accompanied by unpleasant odors.

“Organic waste emits methane, which is a greenhouse gas, and also contaminates groundwater,” explains Professor Golberg. “The treatment of waste is a critical issue. Landfill sites in Israel are reaching capacity, and despite the desire to reduce landfill to a minimum, we are forced to open new sites because there is no other solution. The major advantage of our proposal is that we will reduce the need for so many landfill sites. Municipalities invest considerable funds on waste transportation and treatment, and our solution has the potential to significantly cut those expenses.”

In order to assess the potential of municipal waste in Israel, the researchers analyzed the results of a groundbreaking 2018 survey conducted by E. Elimelech et al. from the University of Haifa. The survey examined the composition of the garbage produced by 190 households in the city of Haifa over the course of a week. The findings revealed that measurable organic waste constitutes about 36.4 percent of food waste and about 16.4 percent of total household waste. In general this organic waste contains around 80% water.

“The results of this survey formed the basis for the waste model in our study,” says Professor Golberg. “We built a continuous reactor — which will eventually be adaptable for solar energy usage — to heat the waste to 280 degrees Celsius [536 degrees Fahrenheit], and we were able to significantly reduce the amount of water and oxygen in the biofuel.

“We found cost-effective catalysts that make it possible to control the ratio between the liquid and solid fuel products. Solid fuel can be used as biochar, effectively sequestering carbon dioxide for extended periods. The biochar can be burned in power plants like regular coal, and liquid biofuels, after upgrading, can power planes, trucks, and ships.”

Using the representative model of the measured organic waste, the TAU researchers successfully produced liquid biofuel with a yield of up to 29.3 percent by weight and solid fuel with a yield of up to 40.7 percent based on dry raw material. This process is versatile and suitable for treating any wet organic waste or residue, for example organic waste from food factories, institutional kitchens, and hospitals.

“The production of biofuels from organic waste components can significantly reduce the volume of municipal waste sent to landfills, thereby decreasing environmental pollution of soil, water, and air,” the researchers conclude. “Moreover, reducing landfilling will lower greenhouse gas emissions and decrease reliance on oil and coal. Converting waste into energy also offers a local solution for Israel’s energy independence and security.”

The researchers acknowledge the support of the chief scientist of the Israeli Ministry of Energy and the company Noga.