Delhi High Court Confirms Patent Rejection for Distillery Waste Recovery Process Citing Lack of Inventive Step

The Delhi High Court has upheld the rejection of a patent application concerning a process designed to recover potassium sulphate and other valuable products from distillery spent wash, an effluent generated during alcohol production. The court found that the claimed invention lacked an inventive step and was essentially a combination of known processes, thereby falling within the exclusion criteria under Section 3(d) of the Indian Patents Act, 1970.

The patent application (No. 201911036748) was filed by Tapas Chatterjee for a process titled “Recovery of Potassium Sulphate and other valuable products from Spent Wash leading to ZLD (Zero Liquid Discharge) System.” The invention disclosed a method to recover multiple useful substances, including potassium sulphate, magnesium sulphate, activated carbon, and reusable water, from distillery spent wash.

The Council of Scientific and Industrial Research (CSIR) filed a pre-grant opposition under Sections 25(1)(b), (e), (f), and (g) of the Patents Act. CSIR argued that the invention was not novel, was obvious in light of existing prior art, lacked inventive step, and was excluded from patentability under Section 3(d) as a mere use of known processes. The opposition primarily relied on two prior art documents: a US patent (referred to as D1) and a BIS Guide (referred to as D2).

Upon examination, the Assistant Controller of Patents upheld the objections, particularly under Section 25(1)(e) for lack of inventive step and Section 25(1)(f) read with Section 3(d). Consequently, the patent application was rejected.

The appellant challenged this decision before a Single Judge of the Delhi High Court, who dismissed the appeal on March 10, 2023. Subsequently, the appellant filed a Letters Patent Appeal (LPA) against the Single Judge’s judgment.

The key issues before the court were whether the claimed invention lacked inventive step under Section 2(1)(ja), warranting rejection under Section 25(1)(e), and whether the invention was excluded from patentability under Section 3(d) as a mere use of a known process.

The appellant contended that the invention was novel and inventive, addressing deficiencies in prior art related to recovering potash-based fertilizers from spent wash. The process involved unique steps such as removing high molecular weight organic compounds from spent wash to obtain a first liquid fraction, concentrating it to a first solid fraction, thermal decomposition to a second solid fraction, dissolving this in a solvent to obtain a second liquid fraction, and recovering potassium sulphate.

The appellant argued that prior arts D1 and D2 did not disclose the complete sequence of steps, nor did they achieve zero liquid discharge (ZLD) or economically recover multiple value-added products. The invention purportedly overcame limitations of existing patents by providing a simple and economical method.

The Assistant Controller’s findings were described as laconic and insufficient to substantiate obviousness from the perspective of a person skilled in the art (PSITA). Regarding Section 3(d), the appellant maintained that the invention was not a mere discovery but a new process resulting in enhanced efficacy, including ZLD and recovery of by-products such as activated carbon and magnesium sulphate.

However, the court upheld the rejection, agreeing that the invention was a combination of known techniques lacking an inventive step and fell within the exclusions under Section 3(d). The Single Judge’s application of the Hoffmann-La Roche test for obviousness was noted, but the court found the invention did not meet the threshold for patentability.

This ruling underscores the stringent standards applied by Indian patent authorities and courts in assessing inventive step and patent eligibility, particularly for processes involving combinations of known techniques and claims of improved efficacy.