Examiner notes that the Office Action dated 11/06/25 has been withdrawn. The new Office Action as follows:
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claim(s) 1-2, 8, 10-13, 16, and 23-25 are rejected under 35 U.S.C. 103 as being unpatentable over Roodbeen (US 2020/0254383) in view of Ainsworth et al. (US 2002/0079266; hereinafter Ainsworth) and Terrien et al. (US 2012/0118011; hereinafter Terrien).
With regard to claims 1 and 10, Roodbeen discloses a system for upgrading biogas through a membrane separation process comprising an anaerobic digester (see paragraph [0037]) configured to generate the biogas from a feedstock containing an organic content (agricultural waste, manure, municipal waste, sewage, food waste, see paragraph [0037]), a first membrane stage (1) configured to separate the biogas into a first residue stream (18), enriched in methane, withdrawn from the residue side of the first membrane stage and forwarded to a second membrane stage (3) as a feed gas therein, and a first permeate stream (20), enriched in carbon dioxide, withdrawn from the permeate side of the first membrane stage, and vented out (at 24), a second membrane stage (3) connected to the first membrane stage in series, configured to separate the residue stream (18) from the first membrane into a second residue stream (32), enriched in methane, withdrawn from the residue side of the second membrane stage and forwarded to a point of use (as a source of energy of fuel, see paragraphs [0003] and [0049]), and a second permeate stream (34), enriched in carbon dioxide, withdrawn from the permeate side of the second membrane stage and recycled back upstream of a gas reservoir (11) at Fig. 1, the abstract, and paragraphs [0003] and [0037]-[0049].
Roodbeen does not disclose the anaerobic digester operating under an operation pressure high than atmospheric pressure, or the second permeate being sent to a compressor and subsequently recycled back to the anaerobic digester.
Ainsworth discloses a system for upgrading biogas comprising an anaerobic digester (see the abstract) configured to generate the biogas from a feedstock containing an organic content, wherein the anaerobic digester operates under an operation pressure higher than atmospheric pressure [10-265 psi (0.7-18.3 bar), 10-100 psi (0.7-6.9 bar), or 25-75 psi (1.7-5.2 bar)], see paragraphs [0043], [0056] and [0071]), and wherein carbon dioxide is separated from the biogas and recycled back to the anaerobic digester to push the thermodynamic equilibrium toward methane production and carbon dioxide consumption (see paragraphs [0066]-[0067]) at Figs. 1-2, the abstract, and paragraphs [0043], [0056] and [0066]-[0071].
It would have been obvious to one of ordinary skill in the art to incorporate the pressurized operation of the anaerobic digester of Ainsworth into the system of Roodbeen to produce higher quality, purer methane, as suggested by Ainsworth at paragraph [0071].
It would have been obvious to one of ordinary skill in the art to incorporate the carbon dioxide recycle to the anaerobic digester of Ainsworth into the system of Roodbeen to push the thermodynamic equilibrium toward methane production and carbon dioxide consumption, as suggested by Ainsworth at paragraphs [0066]-[0067].
Ainsworth teaches introducing the recycled carbon dioxide into the bottom volume of the anaerobic digester using a sparger bar to agitate the digestate sludge phase at Fig. 2 and paragraphs [0065]-[0067], but does not mention a compressor for increasing the pressure of the carbon dioxide.
Terrien discloses compressing (at compressors 17 or 28) a permeate stream (5 or 12) prior to recycling it to a process unit (0) at Fig. 1 and paragraphs [0030], [0040] and [0067].
It would have been obvious to one of ordinary skill in the art to incorporate the permeate compression of Terrien et al. into the system of Roodbeen and Ainsworth to provide any necessary or desired pressure increase of the carbon dioxide enriched permeate for injection into the anaerobic digester.
With regard to claim 11, Roodbeen as modified by Ainsworth and Terrien likewise discloses the corresponding process for upgrading biogas. See again Roodbeen at Fig. 1, the abstract, and paragraphs [0003] and [0037]-[0049], Ainsworth at Figs. 1-2, the abstract, and paragraphs [0043], [0056] and [0066]-[0071], and Terrien at Fig. 1 and paragraphs [0030], [0040] and [0067].
With regard to claim 23, Roodbeen as modified by Ainsworth and Terrien likewise discloses the corresponding process for upgrading biogas. See again Roodbeen at Fig. 1, the abstract, and paragraphs [0003] and [0037]-[0049], Ainsworth at Figs. 1-2, the abstract, and paragraphs [0043], [0056] and [0066]-[0071], and Terrien at Fig. 1 and paragraphs [0030], [0040] and [0067].
In particular, Ainsworth teaches the pressurized anaerobic digester producing biogas having a methane content of 60-100% at paragraph [0062]. The prior art range is seen as overlapping the instantly claimed range. Therefore a prima facie case of obviousness exists in the absence of unexpected or unobvious results.
With regard to claims 2, 12 and 23, the prior art ranges of 10-265 psi (0.7-18.3 bar), 10-100 psi (0.7-6.9 bar), or 25-75 psi (1.7-5.2 bar) are seen as overlapping the instantly claimed range. Therefore a prima facie case of obviousness exists in the absence of unexpected or unobvious results.
With regard to claims 8, 16 and 25, Ainsworth teaches a pH adjusting chemical being added to the pressurized anaerobic digester to control pH, wherein the pH adjusting chemical is sodium hydroxide, lime, sodium carbonate, or sodium bicarbonate (see paragraph [0102]) at paragraphs [0098]- [0102].
With regard to claims 13 and 24, Roodbeen does not disclose the second residue stream from the second membrane stage having the recited methane purity.
Ainsworth teaches producing a treated biogas product to have a methane purity of at least 98% at paragraph [0076].
It would have been obvious to one of ordinary skill in the art to incorporate the product purity of at least 98% methane of Ainsworthinto the system of Roodbeen, Ainsworth and Terrien to provide a high-purity product that can be used for a variety of uses including pipeline injection and as a chemical feedstock without additional purification treatment.
Claims 4-7, 9, 15, 17 and 21-22 are rejected under 35 U.S.C. 103 as being unpatentable over Roodbeen (US 2020/0254383) in view of Ainsworth et al. (US 2002/0079266; hereinafter Ainsworth) and Terrien et al. (US 2012/0118011; hereinafter Terrien), and further in view of Ding et al. (US 2019/0030482; hereinafter Ding).
With regard to claims 21 and 22, Roodbeen discloses a third membrane stage (2) configured to separate the first permeate stream (20) from the first membrane stage into a third residue stream (22) containing carbon dioxide and methane withdrawn from the residue side of the third membrane stage, and a third permeate (24), enriched in carbon dioxide, withdrawn from the permeate side of the third membrane stage and vented out at Fig. 1.
Roodbeen does not disclose the residue stream from the third membrane stage being combined with the permeate stream from the second membrane stage for recycling back to the anaerobic digester.
Ding discloses a system for upgrading biogas through a membrane separation process wherein a retentate stream (50) from a third membrane stage (45) is combined with a carbon dioxide enriched permeate stream (25) from a second membrane stage (30) for recycling at Fig. 2 and the abstract.
It would have been obvious to one of ordinary skill in the to incorporate the combination of the third retentate with the second permeate of Ding into the system of Roodbeen, Ainsworth and Terrien to increase the amount of carbon dioxide recycled to the anaerobic digester to shift the equilibrium towards methane production, as suggested by Ainsworth at paragraph [0067].
With regard to claims 4 and 5, Roodbeen discloses the first and second membrane stages containing a polymeric gas separation membrane having a carbon dioxide/methane selectivity of at least 10 at paragraphs [0042] and [0048].
Ding discloses using polyimides or polyether-polyamide copolymer membranes to separate carbon dioxide and methane, wherein the membranes are composite hollow fibers (see paragraph [0086]) at paragraphs [0034], [0053], [0086], [0088]-[0089], [0096]-[0102].
It would have been obvious to one of ordinary skill in the art to incorporate the polymeric materials and composite hollow fiber geometry of Ding into the membranes to provide membranes having good permeability (thin selective layer) and selectivity and high surface area per unit volume. The Examiner notes that the membranes will exhibit the recited carbon dioxide permeance since they are formed from the same materials and have the same geometry as instantly claimed. Alternatively, forming the membranes to exhibit the recited permeance would have been obvious to one of ordinary skill in the art to ensure carbon dioxide separation from the biogas.
With regard to claims 6, 7 and 15, Ainsworth discloses a recycle gas injector (the sparger bar) configured to inject the compressed stream into the digestate sludge phase in the anaerobic digester, wherein a driving force is provided and controlled to achieve a pressure difference between an exterior and an interior of the recycle gas injector, wherein the pressure of the compressed stream is slightly greater than the operation pressure of the anaerobic digester (positive pressure to allow the carbon dioxide to be injected) at paragraphs [0065]-[0067].
With regard to claims 9 and 17, Roodbeen (see Fig. 1 and paragraphs [0038] and [0052]) and Ding (see Fig. 2) disclose a pressure differential across the membranes to provide a driving force for separation.
Response to Arguments
Applicant's arguments filed 09/29/25 have been fully considered but they are not persuasive. Examiner respectfully maintains that the combination of Roodbeen, Ainsworth and Terrien continues to render claims 1 and 11 obvious for the reasons set forth below.
Applicant contends that the combination of Ainsworth and Terrien with Roodbeen would render Roodbeen’s first gas transport device 14 inoperative, asserting that Ainsworth teaches the use of a pressurized anaerobic digester to elevate operating pressures, while Terrien teaches the use of a compressor downstream of the membrane. Applicant argues that such a combination would teach away from Roodbeen’s intended configuration and purpose.
Applicant further asserts that Ainsworth is directed to an integrated anaerobic digester system for converting cellulose-containing feedstock into useful materials, the system comprising multiple pressurizing anaerobic digesters connected in parallel. Ainsworth discloses operating the digesters at elevated pressures of at least about 10 psi up to about 265 psi, more preferably 10-100 psi, and even more preferably 25-75 psi, during anaerobic digestion of a feedstock slurry ([0043]). Applicant argues that applying Ainsworth’s pressurizable anaerobic digester to Roodbeen’s apparatus 10 would result in inoperability, since Ainsworth’s elevated digester pressure (10-265 psi) would interfere with the operation of Roodbeen’s first gas transport device 14, which operates within a range of approximately 1.5 bar (150 kPa) to 100 bar (10,000 kPa).
Examiner respectfully disagrees. Ainsworth discloses an operating pressure range of approximately 10 psi (0.69 bar) to 265 psi (18.27 bar), which overlaps with Applicant’s claimed operation above atmospheric pressure (14.7 psi), satisfying the claim requirement of operating above atmospheric conditions. Moreover, Ainsworth’s pressure range remains well below Roodbeen’s disclosed pressurization range of 1.5 bar to 100 bar. Accordingly, Roodbeen’s first gas transport device would remain capable of further compressing gas feed originating from Ainsworth’s digester, consistent with Applicant’s own disclosure wherein the compressor increases pressure beyond the operating pressure of the digester, as recited in claims 1, 7, 11 and 15.
Applicant additionally contends that Roodbeen teaches the use of a vacuum pump downstream of the membrane and therefore teaches away from the use of a compressor downstream as in Terrien. However, a prior art reference must be evaluated for all that it teaches and not limited to a single embodiment.
Examiner respectfully disagrees. While Roodbeen does disclose in certain embodiments that vacuum pumps may be used downstream to drive the pressure differential across the membrane, paragraph [0052] expressly states this occurs “in some embodiments,” indicating that alternative configurations are contemplated. Furthermore, Roodbeen clearly teaches the use of compressors or blowers to increase pressure downstream of the membrane stages in other embodiments ([0011]), “may comprise a compressor or blower,” and [0038], “the transport device 14 may be…a mechanical device that adjusts (e.g., increases) pressure”). Therefore, Roodbeen does not teach away from the use of compressors as described in Terrien. The combination of Roodbeen, Ainsworth, and Terrien continues to render the claimed subject matter obvious.
Applicant further argues that Ding is directed to a process for recovering methane from digester biogas or landfill gas, and more specifically to a method for producing biomethane by removing impurities from compressed digester biogas using staged membrane modules of at least two different types, resulting in a biomethane having at least 94% CH4, less than 3% CO2, and less than 4 ppm H2S. Applicant asserts that since Ding does not disclose an anaerobic digester, it cannot remedy the alleged deficiencies of Roodbeen.
Examiner respectfully disagrees. Ding was cited solely to demonstrate a system of upgrading biogas through a membrane separation process in which a retentate stream (50) from a third membrane stage (45) is combined with a carbon dioxide-enriched permeate stream (25) from a second membrane stage (30) for recycling, as shown in fig. 2 and described in the abstract. This configuration is known in the art and was relied upon only for this teaching. It is the combination of the cited references, rather than any single reference alone, that renders the claimed invention obvious.
All other arguments presented by Applicant have been fully considered but are deemed persuasive.
Conclusion
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/DUNG H BUI/ Primary Examiner, Art Unit 1773