‍Introduction: The  Sustainability Dilemma
Sustainability has become a critical concern for businesses, but deciding how to resource it can be challenging – especially for medium-sized enterprises. UK today face growing expectations to cut carbon, reduce waste, and report on ESG (Environmental, Social, Governance) performance. In fact, an overwhelming 91% of mid-sized UK businesses (10–249 employees) now have a formal sustainability strategy in place or in development. The question is, who will carry out that strategy? Companies often debate between hiring an in-house sustainability team versus engaging external sustainability consultants.

For a medium-sized business with limited budgets and manpower, there are pros and cons to each approach. Data shows that relatively few companies have large dedicated sustainability departments – only about 7% do – while nearly a third assign sustainability tasks to staff on top of their other roles​ Many businesses therefore turn to outside consultants for specialized help. This article will compare the two routes in depth, focusing on the reality of UK SMEs. By understanding the trade-offs, you can determine the best approach for your business’s sustainability journey.

The Case for an In-House Sustainability Team

Building an in-house sustainability capability means hiring employees (or assigning existing ones) to manage sustainability from within your organisation. For a business, this might start with a single Sustainability Manager or a small team rather than a full department. What are the advantages of keeping it in-house?

Pros of In-House Staff:

• Deep Internal Knowledge: An internal team member lives and breathes your company every day. They understand your operations, culture, and context intimately. This means they can integrate sustainability initiatives seamlessly into business processes. For example, an in-house sustainability lead can work daily with your operations team to tweak processes, monitor data, and engage colleagues in a way an external person might not easily do.
• Continuous Presence and Alignment: Sustainability isn’t a one-off project – it requires ongoing effort. Having someone on staff means there’s continuous ownership. They can respond in real time to issues or ideas that come up. Over time, they also become a champion for sustainability internally, keeping it on the agenda at meetings and decision-making forums. Their constant presence can help embed sustainability into the company culture.
• Tailored to Company Values: An employee can embody your company’s values and speak the internal language. They are viewed as part of the team. This can make colleagues more receptive to sustainability initiatives (versus seeing it as advice from an outsider). An in-house person can build relationships across departments – from finance to marketing – to advocate for sustainable practices in a way that aligns with internal priorities.
• Long-term Perspective: Employees have a long-term stake in the company. They can plan multi-year strategies and see them through implementation over time. This continuity is beneficial for initiatives that unfold gradually (e.g. a 5-year net zero roadmap). There’s no risk of the engagement ending because, as staff, their job is to keep pushing forward.

However, hiring internally also has significant challenges:

Cons of In-House Staff:

• Higher Fixed Cost: Bringing on a full-time sustainability manager is a substantial commitment. In the UK, salaries for sustainability professionals can range from ~£25k for junior roles up to £50–60k+ for senior experts​ plus benefits and overhead.This is a major addition to payroll. If your sustainability needs are not full-time, you may be under-utilising an expensive resource during quieter periods.
• Skills Breadth Limitations: Sustainability is broad – it covers environmental science, regulatory compliance, stakeholder engagement, reporting, and more. It’s hard to find one person who is an expert at everything. Large companies have teams covering different areas, but a single sustainability officer might struggle to handle, say, detailed carbon accounting and community outreach and legal compliance all alone. There may be knowledge gaps that require external training or support regardless.
• Recruitment Challenge: Finding the right person can be difficult. There’s high demand for experienced sustainability professionals as companies race to build these roles (a recent survey noted companies are “busier than ever” adding sustainability roles​). Businessses might have less attractive budgets or career progression compared to big firms, so attracting talent is competitive. It can take months to hire, and a wrong hire sets you back significantly.
• Retention Risk: If your lone sustainability specialist leaves the company, their expertise and momentum go with them. This is a real risk – sustainability is a hot job market, and turnover can happen. An business could find itself without knowledge continuity if an employee resigns.
• Operational Bias: Sometimes an internal person can become siloed or face internal politics. They might feel pressure to align with existing corporate narratives, possibly downplaying issues that an independent voice would call out. An external consultant can often speak more freely about tough issues like necessary investments or policy changes, whereas an employee might be more constrained.

In summary, an in-house role offers integration and constant focus but at a higher fixed cost and potential skill limitation.  Hiring in-house tends to make sense if sustainability is becoming core to your business’s mission or operations – enough to justify a permanent role. Many medium businesses start considering an internal hire when their sustainability workload becomes too large or continuous for existing staff to juggle.

The Case for Hiring a Sustainability Consultant

Now let’s look at the alternative: outsourcing to a sustainability consultant or consultancy. This could mean hiring a freelance consultant, a specialist from a platform like Leafr, or a consulting firm, typically on a project or part-time basis. What benefits can an external sustainability consultant bring?

Pros of External Consultants:

• Specialist Expertise on Demand: A key advantage is flexibility in expertise. You can bring in a consultant with exactly the skill set you need, exactly when you need it. For example, if you require a carbon footprint and reduction plan this quarter, you can hire a carbon specialist for that project. Later, if you need help engaging employees or suppliers, you might engage a different expert. You’re not limited to one person’s capabilities. Consultants often have years of experience across multiple companies, so they come with a toolkit of what works and what doesn’t in practice. As one sustainability consultant described, their role is to help businesses navigate a landscape that’s constantly changing​ – tapping into their broader perspective can accelerate your progress.

• Cost Flexibility: With consultants, you pay for what you need and no more. This is vital. Instead of a full salary, you might pay a consultant for, say, 20 days of work spread over a few months. If your needs are seasonal or project-based, this can be far more cost-effective. Many SMEs use consultants to kick-start sustainability efforts (at a manageable cost) before deciding if a full-time role is justified. Additionally, there are no long-term employment costs (pension, etc.) and if budgets tighten, you simply pause or end the consulting engagement.
• Quick Access and Faster Start: Hiring a consultant can usually be done faster than recruiting a new employee. Consultants are often available to start within weeks or even days, whereas employee recruitment can take months. If you have an urgent sustainability deadline – for example, preparing your first ESG report for investors or complying with a new regulation – a consultant can step in immediately to help meet it. They also require less hand-holding on general sustainability know-how, since they’re already experts, so you gain speed in ramping up your initiatives.
• Objective External Perspective: An outside consultant brings a fresh pair of eyes. They can spot sustainability opportunities or risks that insiders might overlook. Because they aren’t tied to internal politics or status quo, consultants are well placed to challenge “the way we’ve always done things.” For instance, a consultant might identify inefficiencies or bold changes (like switching to a renewable energy provider or rethinking your product materials) and push for them in a constructive way. This objectivity can be particularly valuable if there’s skepticism or inertia internally – an external voice citing industry best practices can build the case for action.
• Scale as You Go: Consultants can serve as a bridge as your sustainability program grows. Early on, a few days of consulting advice might suffice. As you progress, you can increase the engagement (or add more specialized consultants). Some business's eventually build up to needing a full-time person, but using consultants initially allows you to scale up commitment gradually. This approach ensures you’re not over-investing before sustainability work has proven value in your business.

Of course, engaging consultants has downsides too:

Cons of External Consultants:

• Limited Availability & Internal Presence: A consultant, no matter how good, is not embedded in your company every day. They will divide time among clients. For business's that need a lot of hand-holding or quick daily decisions, this could be a disadvantage. There may be delays if the consultant is on another project or only scheduled on certain days per week for you. Also, because they’re not on-site full-time, they might miss some day-to-day context or informal discussions where ideas emerge.

• Knowledge Transfer Required: The consultant will need to be brought up to speed on your business operations, data, and culture whenever they start a project. This onboarding takes effort on both sides. And when the project ends, if they step away, you need to ensure all knowledge (like methodologies, calculations, contacts established) is transferred back to your team. If not managed, there’s a risk that know-how leaves with the consultant.

• Perception by Employees: Sometimes employees might be wary of “outsiders” coming in to drive change, especially if sustainability requires altering processes or extra work for departments. It’s important to introduce consultants in a way that positions them as a partner, not a critic. When done right, consultants often engage staff just as effectively, but it’s a factor to consider – internal folks might initially be more receptive to a colleague leading sustainability than an external advisor. Strong communication and involving an internal sponsor can mitigate this.

• Continuity and Follow-through: Consultants typically deliver recommendations or initial implementations. After their engagement, sustaining the effort is up to the company. If there isn’t an internal person accountable, there’s a risk that once the consultant’s project wraps up, progress stalls. For example, a consultant might deliver a great sustainability action plan, but six months later, how much is executed? Business's need to have a plan (perhaps a part-time internal champion) to carry the torch between consultant engagements.

• Variable Quality and Fit: Just as with hiring an employee, not every consultant will be the right fit. There’s a possibility of hiring someone who doesn’t deliver to expectations or doesn’t gel with your team, and by the time you realize, the contract may have progressed. However, using a vetted source (such as Leafr’s network of pre-vetted consultants) can reduce this risk by ensuring you start with reputable professionals.

In essence, consultants offer expertise and flexibility that align well with the needs of many business's. They allow you to access top-tier knowledge for specific needs without the commitment of an employee. This makes them ideal for tackling defined projects (like carbon audits, certification processes, or strategy development) or providing interim support until a business grows further.

Comparing Costs: Consultant vs. Employee

Cost is often the deciding factor when weighing these options. How does the financial side stack up between hiring a consultant and employing someone in-house?

• Upfront and Ongoing Costs: A full-time sustainability manager might cost, say, £50,000 per year (roughly £4,167 per month) plus employer on-costs. If your sustainability initiatives could be handled in, for example, 50 days of work spread across a year, an external consultant might charge around £500 per day – totaling £25,000 for that work. Even if the consultant’s day rate seems high, you often need far fewer days than a full-time employee’s year-round availability. For sporadic or project-based needs, consultants clearly save money.

• Hourly/Day Rate vs. Salary: Let’s break down an example: A mid-level UK sustainability consultant’s average daily rate is around £500–£600​. That’s roughly £62–£75 per hour. Meanwhile, an in-house sustainability officer on £45k/year is about £24 per hour (assuming 7.5 hour days, 250 workdays/year). At first glance, the consultant is more expensive per hour. However, remember the consultant’s hours are used only as needed. If you only require ~10 hours of specialist work per month, paying a higher rate for those hours is more economical than employing someone 160 hours a month. The utilisation is the key factor.

• Hidden Value of Expertise: Consultants often operate more efficiently due to experience. A skilled consultant might complete in one day what could take an inexperienced internal hire a week to figure out. They come with tools, templates, and knowledge that accelerate the work. Thus, even though their rate is higher, the total hours required could be lower. Consider this when comparing costs – it’s about cost for the outcome, not cost per hour alone.

• Scaling and Commitment: With an employee, you’re locked into ongoing costs regardless of how priorities change. With a consultant, you can scale budget up or down. For instance, maybe Year 1 you invest £20k in consulting to set up a sustainability framework and quick wins. In Year 2, you might only need £5k for occasional check-ins or annual reporting assistance because a lot of work is done. If you had hired an employee, you’d be paying salary both years. Consultants give you that scalability in spend aligned to your sustainability roadmap maturity.

• Opportunity Cost: Also think about the opportunity cost of not getting expert help. If not addressing sustainability properly leads to lost contract opportunities (many large customers now require suppliers to have sustainability credentials) or compliance fines, that carries a cost. A consultant might prevent those losses by keeping you on track. Similarly, an internal person might be diverted to other company duties in crunch times (wearing multiple hats), whereas a consultant’s mandate is clear – so some tasks might only get done with a consultant’s involvement.

In financial terms, smaller business's or those just starting on sustainability typically find consultants more cost-effective, whereas a larger medium-sized firm with extensive ongoing sustainability work might reach a point where hiring in-house yields better value. It can be useful to forecast a 1-2 year budget for both scenarios: what does two years of a consultant (for defined projects) look like vs. two years of an employee (with all overhead)? This exercise often illuminates the best path.

When an In-House Team Makes Sense

For some medium-sized businesses, investing in an in-house sustainability role or team is ultimately the best choice. Here are scenarios where hiring internally is advantageous:

• Sustainability is Core to Your Value Proposition: If your business’s brand and success heavily rest on sustainability (e.g. you market yourselves as an eco-friendly product company, or you operate in a heavily regulated industry like waste management or renewable energy), having in-house expertise is almost essential. You’ll need daily decision-making with sustainability in mind, which is tough to do if guidance is external. An internal champion ensures sustainability is woven into every facet of operations and strategy.

• Growing Regulatory Burden: Perhaps your company is nearing thresholds that will impose mandatory requirements – for example, closing in on 250 employees or expanding turnover, meaning large company regulations will apply soon. If you anticipate that compliance with UK regulations like SECR, mandatory climate risk disclosures, or extensive reporting is on the horizon, an in-house hire can build systems proactively. They will manage continuous compliance tasks better than ad-hoc consultant visits.

• Frequent Sustainability Activities: If you find that sustainability-related tasks are cropping up every week – from answering customer questionnaires about your carbon footprint, to finding ways to cut energy costs, to internal sustainability campaigns – that steady stream of work could justify a dedicated role. Essentially, when sustainability becomes a daily operational consideration, you need someone available daily.

• Desire to Build Internal Capacity: Over time, companies may prefer to own the knowledge internally. By hiring and developing staff, you ensure that know-how and skills remain in-house, building your company’s capabilities. This is a long-term strategic decision: you are investing in building an internal knowledge base so that eventually you rely less on external help. For example, you might use a consultant initially, but as your team learns, you decide to bring those skills inside and run things directly.

• Leadership and Culture Change: If a key goal is to transform your company culture to be more sustainable, having an internal leader spearheading that change can be very effective. They can engage with colleagues every day, lead by example, and rally the troops in a way an external party might struggle to sustain. An employee can also navigate internal change management more delicately, understanding personalities and what motivates your people. If you foresee heavy internal engagement – forming green teams, doing workshops, integrating with HR for training programs – an in-house sustainability coordinator might be best.

Importantly, it doesn’t have to be an all-or-nothing initial commitment. Some 'busness's start with a part-time internal role (perhaps someone who splits time between sustainability and another function like operations or compliance). As the sustainability program grows, that role can expand to full-time. In other cases, companies create a cross-functional team (an informal group of employees from different departments) to handle sustainability collaboratively, possibly supported by periodic consultant input. This hybrid approach can be a stepping stone to a future formal sustainability team.

When a Consultant is the Right Choice

On the other hand, there are many scenarios where sticking with external sustainability consultants (at least for the time being) is the smarter route:

• Early Stage of Sustainability Journey: If you are just beginning to address sustainability in a structured way, a consultant can help you develop a roadmap and achieve early wins. At this stage, you may not even know the full scope of what you need long-term. A consultant’s assessment can clarify this. It’s often prudent to use consultants to establish your baseline (e.g. measure your carbon footprint, identify compliance gaps, set initial targets). They can create a solid foundation without the commitment of a hire before you’re ready.

• Specific Projects or Expertise Gaps: Maybe you have a competent internal team handling day-to-day environmental efforts, but a specific project exceeds your expertise. For instance, implementing a life-cycle assessment for a product, or preparing a complex sustainability report in line with GRI standards, or navigating a one-off certification process (like PAS 2060 for carbon neutrality). For these defined tasks, bringing in a consultant with deep expertise yields better results than diverting your team or hiring someone new for a short-term need.

• Temporary or Interim Needs: Sometimes you may plan to hire an in-house person eventually, but need help right now. Consultants can act as an interim solution. For example, if your company has announced a net-zero goal and needs a strategy outlined in the next 6 months, a consultant can develop that strategy while you take the time to find the perfect permanent hire to implement it. In fact, some consultants specifically offer “fractional sustainability officer” services – working a set number of days per month as a stand-in sustainability manager for companies that aren’t ready to hire full-time. This arrangement gives you the benefits of both worlds to some extent.

• Budget Constraints: If your budget for sustainability this year is, say, £10,000, that clearly won’t fund a qualified full-time salary, but it could buy a significant amount of consulting support. Many business's simply cannot afford a dedicated hire yet, and it’s far better to use that budget to get expert guidance as needed than to postpone sustainability efforts altogether. Consultants enable you to make progress within tight financial limits.

• External Pressure and Credibility: Sometimes, external stakeholders might be more reassured by seeing that you’ve engaged recognized experts. For example, if investors or major clients are scrutinizing your sustainability, being able to cite that you worked with a reputable sustainability consultant or firm can add credibility to your plans. It shows you’re serious enough to bring in outside expertise. While an internal person also shows commitment, a known external advisor can carry weight in certain situations (like assurance of data or validation of targets).

In short, consultants shine when you need targeted expertise, flexibility, or a quick start without long-term binding. Many UK business's find that consultants help them reach a level of sustainability performance that later justifies a permanent team once the value is proven. There is no one-size-fits-all answer, but if any of the above scenarios ring true, leaning on consultants is likely the best path for now.

The new way - a hybrid approach

When it comes to building sustainability capacity, the question doesn’t have to be in-house or consultant. The most forward-thinking businesses are adopting both.

A hybrid model combines a strategic internal core with flexible access to external sustainability expertise. For many medium-sized businesses, this isn’t just a tactical solution, it’s a strategic choice that balances continuity, cost-efficiency, and specialist input.

Build a strategic core

A common approach is to appoint a Sustainability Champion from your existing team. This person may already lead operations, HR, or compliance, and spends 10 to 30 percent of their time driving the sustainability agenda.

Their role is not to be the expert on every ESG issue. Instead, they act as the internal anchor:

• Coordinating across departments
• Maintaining momentum
• Translating strategy into action
• Liaising with external consultants
• Reporting to senior leadership

This internal role ensures sustainability is not just an external project but is embedded into day-to-day decisions and culture. It keeps progress on track and ensures accountability sits inside the business.

Plug in expertise when you need it

Alongside this internal core, companies use on-demand sustainability consultants to bring in technical depth and strategic insight.

These experts are brought in for:

• Carbon accounting and net zero roadmaps
• Regulatory compliance (e.g. SECR, CSRD, ESOS)
• Materiality assessments and stakeholder engagement
• ESG policy development
• Data strategy, reporting, and assurance prep

You can engage consultants for a one-off project or on a retainer basis, where they provide a few days of input each month and function like a fractional Head of Sustainability.

They attend meetings, guide implementation, answer ad hoc questions, and ensure you stay aligned with best practice and emerging regulation. This gives you access to high-calibre sustainability leadership without the full-time salary.

Platforms like Leafr make this easy by connecting businesses to vetted experts open to flexible engagements.

Why this hybrid model works so well

A hybrid model is not a compromise. It is a deliberate strategic structure that gives your business the ability to scale, adapt, and execute sustainability work effectively. Here’s what it offers:

• Strategic internal coordination
  Keeps sustainability embedded in daily operations and decision-making, ensuring it doesn’t sit in a silo or get deprioritised.
• Cost-efficient external expertise
  Gives you access to high-value specialist support only when you need it, without the fixed cost of a full-time team.
• Faster progress
  Avoids the delays and overhead of long hiring cycles or trying to build deep in-house capability from scratch.
• Flexibility
  Allows you to scale support up or down depending on your project pipeline, funding, or reporting cycle.
• Long-term resilience
  Helps you build internal ownership and continuity while still bringing in fresh thinking, innovation, and specialist insight from outside.

Together, these benefits make the hybrid model an ideal setup for medium-sized businesses looking to move quickly, stay lean, and still operate with best-in-class sustainability leadership.

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This approach lets you punch above your weight. You gain access to specialists with deep experience, while building internal knowledge and credibility over time.

Some companies evolve this model into a fully in-house team. Others keep the blend because it works so well.

There is no rule that you must eventually choose one route over the other. The hybrid model grows with your business and budget.

Real-world examples

One Leafr client, a 150-person B2B services company, appointed their Head of Ops to lead sustainability part-time and retained a carbon expert 2 days per month. Over 6 months, they completed a footprint assessment, introduced supply chain KPIs, and launched a sustainability policy. No full-time hire. Just smart resource use.

Another SME in manufacturing worked with a consultant on retainer to guide B Corp preparation, while their internal lead handled team engagement and documentation. They made more progress in 4 months than they had in 2 years of trying alone.

Final Thought: This Is How You Build a Scalable, Resilient Sustainability Function

The hybrid model is about more than cost or convenience. It is about deliberate resourcing. You retain strategic control internally while leveraging experts for specialist tasks and surge capacity.

This approach:

• Builds internal capability
• Reduces reliance on any single person
• Provides clarity to boards and regulators
• Unlocks flexibility without sacrificing expertise

At Leafr, this is the model we believe in. It’s how we’ve helped clients reduce costs by 60 percent, accelerate progress, and still retain full ownership of their sustainability journey.

You don’t need to choose between too little support and too much overhead. You can design a setup that is lean, smart, and built for growth. A strategic core supported by fractional experts is often the sweet spot.

Want Help Designing a Hybrid Sustainability Team?

We can help you:

• Identify your internal champion
• Match with vetted consultants for fractional roles
• Structure a clear scope and rhythm for the hybrid model
• Evolve toward a full internal team over time, if desired

Check out our client stories or explore available consultants on Leafr. You might find the perfect sustainability partner can start next week, not next quarter.

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