Transport Refrigeration Units (TRUs) play a crucial role in the cold chain industry, but their diesel emissions contribute to climate change and public health risks. With increasing global focus on sustainability, transitioning to active diesel particulate filter (DPF) technology—including DPF retrofit systems—has become an essential part of meeting environmental, social and governance (ESG) goals.
In this article, we’ll explore the current landscape of TRU emissions compliance, compare the benefits of retrofitting existing units versus replacing them with new models, and outline practical steps to guide your transition.
The current scenario
It’s estimated over 250,000 TRUs operating nationwide release over 0.1 grams per brake-horsepower hour (g/bhp-hr) of diesel particulate matter (DPM) into the environment. While many businesses have set targets to achieve zero emissions in the future, it’s important to consider the here and now — diesel engines will remain part of the industry for many years to come.
According to Fleet Equipment Magazine, although electric truck orders are opening across the board from many truck OEMs, the hard fact is most fleets (especially for on-highway, long-haul applications) will be operating diesel for the near future.
This is where investing in an active DPF system provides an immediate path to compliance and measurable emissions reduction without waiting for full electrification.
Following emissions standards within the state of California
For TRU fleets operating in California, there is an added layer of importance regarding transitioning to active DPF technology. The California Air Resources Board (CARB) has set stringent regulations and deadlines fleets must meet to comply with emissions standards.
Due to the nature of these regulations, businesses must stay current with ongoing CARB updates and industry news related to their fleet’s transition. Companies that do not follow the regulations could face stiff fines or other penalties, so it is crucial for businesses operating in California to take all the steps necessary for compliance.
The CARB website provides fleet owners access to tools such as TruckStop, which helps identify eligible vehicles for retrofitting or replacement as well as other incentives available from local governments.
Complying with emissions standards in other states
Even if your company operates TRUs outside California, it’s crucial to ensure your fleet meets the 0.02 g/bhp-hr PM emissions standard. Fortunately, there are new TRUs available in the market that meet this standard, and retrofitting existing TRUs with verified active DPF systems is readily achievable. Rypos active DPFs offer a seamless solution which doesn’t require driver intervention and is compatible with popular TRU brands like Thermo King® or Carrier®.
The benefits of active DPF technology
TRUs can emit up to 29 times more carcinogenic particulate matter (PM) and six times more nitric oxides (NOx) than larger, modern diesel truck engines. Rypos’ active DPF technology can reduce PM emissions from heavy-duty diesel engines by more than 90% — immediately.
Rypos’ ULETRU DPFs produce an impressive 10-12 cumulative metric tons of CO2e credits per year and over 150 metric tons of CO2e credits for the life of a diesel TRU.
These measurable reductions make DPF retrofits one of the fastest, most cost-effective ways for TRU fleets to align with CARB regulations and corporate sustainability goals.
TRU fleet operators face two clear options: retrofit existing diesel units with DPF systems or replace them entirely with new, compliant TRUs. Each path offers distinct advantages in terms of cost, timing, and long-term sustainability strategy.
What is a DPF retrofit?
A DPF retrofit is the installation of an aftertreatment system designed to capture and oxidize particulate matter from an existing diesel engine’s exhaust. Unlike passive filters, which rely on exhaust heat to self-clean, active DPF retrofit systems use electrically powered regeneration to maintain full filter performance even in stop-start, low-load duty cycles typical of TRUs.
In short, a retrofit DPF system upgrades your current diesel TRU to perform like a newer, cleaner model, reducing black carbon emissions by up to 95% without replacing the engine. These systems are engineered for reliability, verified by CARB and designed to help operators achieve near-zero particulate emissions today.
Retrofitting versus purchasing new TRUs – which is right for you?
Choosing between retrofitting your existing TRUs and purchasing new units depends on asset age, budget and compliance timelines. Retrofits can accelerate near-term compliance with less disruption, while new units provide the latest engine platforms and warranty coverage.
Use the comparison below to match each path to your operational goals.
Retrofit existing TRUs
Pros
- Lower upfront capital than full replacement—lets you move more units into compliance sooner.
- Works in real-world duty cycles when you select an active DPF retrofit system that regenerates at any load, without driver intervention.
- Faster rollout: easy to pilot on a subset of units, validate performance and scale up.
- Immediate environmental impact
Cons
- Integration and packaging must be properly engineered; passive-only systems may not regenerate consistently and can increase maintenance.
- Older engines remain less efficient—you won’t gain the incremental fuel savings of the latest model year.
- Timing matters: if a TRU is near a CARB life limit or model-year phase-out, a retrofit may offer a shorter return window.
Purchase new TRUs
Pros
- Access to the latest emissions technology and manufacturer warranties.
- Better long-term planning with standardized equipment and integrated emissions control systems.
- Aligns with future zero-emission strategies and long-range ESG targets.
Cons
- Highest upfront investment—can be difficult to justify if many assets are mid-life.
- Lead times and onboarding may disrupt operations.
- Possible stranded value if you replace units that could have been CARB-compliant through retrofit.
Quick decision guide
Choosing between retrofitting and purchasing new TRUs ultimately comes down to your budget, compliance timeline and the current condition of your assets. If your fleet is operating under tight capital constraints or needs to achieve near-term emissions compliance, a retrofit is often the most practical path. Active DPF retrofits, especially those that regenerate at any load, allow fleets to meet emissions standards quickly and cost-effectively, while keeping existing assets in service.
Conversely, if your TRUs are nearing the end of their lifecycle or model-year limits, investing in new units can provide long-term value through improved engine efficiency, warranty coverage and alignment with future zero-emission goals.
For companies uncertain which path to take, piloting a small retrofit program can provide real-world data on installation time, maintenance needs and emissions outcomes before committing to a full-fleet transition.
Three steps to an actionable active DPF transition plan
Transitioning to active DPF technology is a significant opportunity for companies to demonstrate environmental consciousness through tangible steps to reduce emissions. It allows businesses to meet their ESG goals and promote environmental consciousness as part of company culture. It is also an excellent way to “future proof” your company as emissions regulations continue to tighten as we move toward net zero goals.
Whether you chose to retrofit or replace your TRU units, here are three actionable steps to making the switch:
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Understand emissions
Educate yourself on TRU emission tiers and available retrofit technologies. Major TRU providers offer both clean and legacy diesel options. Obtain quotes from CARB-verified DPF retrofit manufacturers or TRU OEMs for both retrofit and replacement scenarios.
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Promote your commitment to clean air
Beyond meeting ESG goals, clean-air investments enhance brand value and employee engagement. Document sustainability progress in your ESG report and communicate results to your stakeholders and customers.
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Create a financial plan
Develop a phased funding approach to spread costs. Look for grants, loans, or state-level CARB retrofit incentives that can offset installation expenses.
Moving forward with active DPF technology for your TRU fleet
Transitioning to active DPF retrofit systems for TRU fleets is a wise decision beneficial for both the environment and business operations. By actively reducing diesel emissions, TRU fleet owners contribute to a cleaner future and protect the health of communities. This tangible effort in combating climate change improves the overall sustainability profile of businesses, enhancing reputations and attracting environmentally conscious partners, investors and customers.
By equipping TRUs with Rypos’ DPFs, fleet owners can achieve up to a 95% reduction in black carbon emissions, making measurable progress toward sustainability and compliance goals today. Contact our team to explore the right retrofit strategy for your fleet.
