What Can We Do with Spent Bleaching Earth?

This week Government Regulation No. 22 of 2021 has been issued, which revokes the Government Regulation No. 101 of 2014, ruling that spent bleaching earth (SBE), a discarded palm oil refinery from the degumming and bleaching process no longer characterized as hazardous and toxic waste in Indonesia. This decision provokes criticism from various parties, especially environmentalists, as SBE contains several heavy metals, which, if not properly managed, will cause negative impacts on the environment and human health.

 These significant changes become urgent homework for the palm oil industry player and researcher in Indonesia to turn this unfavorable and potentially harmful decision into a win-win solution both economically and environmentally.

Spent Bleaching Earth (SBE)

Spent bleaching earth (SBE) is one of the major wastes from the palm oil industry. To imagine how many SBE are generated in a year, let us look at Indonesia’s annual production in 2020 of crude palm oil (CPO) (according to Council of Palm Oil Producing Countries), which is about 44 million tonnes. The bleaching earth dosage used is about 1% of CPO weight, which will produce as much as 39,600 tons of SBE every day. Can you imagine the excessive waste of SBE produces in a year?

The degumming and bleaching process in pretreatment of crude palm oil uses bleaching earth, mainly containing silicon dioxide. After the process, a huge amount of SBE is generated. According to an analysis conducted by Widyawati and Ufidian (2017), SBE contained several heavy metals, including Al (10.74%), Fe (6.89%), Pb (20.18 ppm), Ni (8.74 ppm), and Cu (23.52  ppm). The contamination of heavy metals in the soil will affect the quality of the plant and yield. Not only that, it will harm the microbial too. Furthermore, the contamination of heavy metals in the aquatic environment will endanger marine organisms.

SBE also contains a high percentage of residual oil, around 20 – 40%, which must be carefully handled since it is highly flammable. Moreover, it has a foul odor from the clay minerals and the residual oil. Generally, SBE is burned or disposed to landfills after doused with water to reduce the fire's nature. Incineration causes air pollution and hazard and is associated with greenhouse emissions (GHG). Therefore, to overcome these adverse impacts at present and in the future, it is necessary to develop new effective and efficient technologies for SBE disposal and the utilization of SBE into a more functional and valuable product.

What can we do to the SBE?

What to do with SBE has been the subject of researches for decades. According to Wan et al. (2019), bleaching earth (Al2O3 and SiO2 as the main component) is commonly used to decolorize oil in the edible oil refining process. After the refinery, the activated bleaching earth lost its activity and became waste known as spent bleaching earth (SBE). SBE contains the original activated bleaching earth and ~30% oil. The removal of additional oil is the crucial key to the reusability of SBE.

Generally, SBE has been used in the oil industries to treat and remove poisons and dyes from raw oil. Researches have been conducted regarding the application of SBE, and most of the application is as adsorbent, such as fluoride removal from groundwater and cheap carbon precursor in organic dye removal. SBE can also improve the quality of building materials, including cement replacement in concrete products, non-fired wall tiles, aggregates replacement in concrete mixture, and pozzolan materials.

Studies have found that SBE has potential as the new material of lightweight composite products for the construction field. In bioenergy, SBE can be used for biodiesel purification and can also act as a catalyst in the transesterification process of waste frying oil. Other attempts on SBE utilization as fertilizer, lubricants, and as a substrate for the spawn production of shitake mushroom. Further research also tried to ferment oil-containing SBE to be used in medicine, food, and fodder industries. One alternative idea that the industry could perform is to make fuel briquettes by mixing the SBE with some maltodextrin and compressing the mixture. The resulting briquettes have about the same calorific value as wood briquettes.

Nevertheless, the downgraded level of spent bleaching earth to non-hazardous and toxic waste will be directly related to its waste management. The waste management will be looser and cheaper. It is undoubtedly good news for the palm oil industry player in Indonesia.  However, they should not be ignorant of the SBE disposal in the future. A thoughtful and thorough waste management plan should be designed, and collaboration between industry and research centers, and universities should be further enhanced to achieve more environmentally friendly waste management control in Indonesia.