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From property portfolios and home builders to multinational corporations and governments, commitments to get a grip on carbon emissions are multiplying. But the plethora of terms can get a little confusing, for example, is net positive the same as carbon negative?

Here’s a handy guide to the most commonly-used terms.

Net zero energy

There are two ways of looking at this. The first is based on simple maths and means a building, precinct, process or region generates as much energy within its own boundaries or site as it pulls in from elsewhere over a specific period – most often a year.

The other definition is a building or precinct or region that generates 100 per cent of its own energy needs on site or within its boundaries.

Image from World Resources Institute

The World Green Building Council notes the latter isn’t feasible for many buildings or sites, so it has focused on pathways for buildings to be both energy-efficient and meet energy needs from either offsite or onsite renewables.

A big game-changer has been the uptake of renewable energy storage, both at the micro scale with home batteries, and at the macro scale, such as South Australia’s giant Tesla battery or the projects under construction in the pumped hydro and compressed air storage space.

We have heard numerous stories in the past couple of years of both households and businesses that are operating at net zero for energy due to a combination of energy-efficiency, renewables on-site and renewable energy storage.

Mirvac is also in the early stages of a project supported by ARENA, which will deliver a precinct of net zero energy townhouses in Melbourne.

City of Sydney is building on research conducted by pitt&sherry that showed Net Zero apartment buildings are feasible, launching a Net Zero Energy discussion group at LinkedIn to bring together industry stakeholders including developers, consultants and state and local government planners to advance a pathway. Read more here.

Arup has also undertaken some research into the basic principles of designing for net zero.

Net positive energy

When a building or precinct generates more energy than it uses and shares that energy through either a local microgrid or by sending it into the main grid, it becomes energy positive.

Ideally, a project aiming for Living Building Certification achieves at least a small percentage of energy surplus as part of Net Positive Carbon Energy petal.

It is not impossible to achieve, as some of the projects at Monash University led by Dr Robin Brimblecombe have shown. He and Dr Kara Rosemeier’s Positive energy homes is a step-by-step guide to design and build net positive dwellings. It also highlights case studies of how it has been achieved by some Australian homes.

Other examples include Positive Energy Places, a commercial building in Melbourne and the Sustainable Buildings Research Centre in Wollongong, which was the first major building in Australia to achieve Living Building certification.

On a wider scale, Mirvac is aiming to achieve net positive energy across its entire portfolio and operations.

Carbon negative

Carbon negative is used for larger scales than individual buildings, such as precincts, regions, businesses or even entire nations. It means absorbing more carbon than all combined carbon emissions within the specific area or operation.

According to the Climate Council, Bhutan is the only nation on earth that is carbon negative. It relies extensively on renewable hydroelectricity, and exports a substantial percentage of it to India, and it also has extensive carbon sinks in the form of forests and agricultural lands.

Figures show Bhutan generates only 1.1 million tonnes of carbon dioxide annually, and its forest sequesters much more than that amount annually.

This means they are a net carbon sink for millions of tonnes of CO2 each year. Additionally, Bhutan exports most of the renewable electricity generated by its fast-flowing rivers to India, driving the country into carbon negative status. At this rate, by 2020, Bhutan will be exporting enough electricity to offset 17 million tonnes of CO2 annually.

It’s become a big, hairy audacious goal for some big companies to aim for. Microsoft, for example, announced in January it was aiming for carbon negative by 2030.

Growing trees and building soil carbon on agricultural lands are two approaches the International Energy Agency has identified as sound options for achieving carbon negative status. Others include bioenergy with carbon capture and storage, and also direct air capture.

Carbon neutral

Carbon neutral is basically a balancing act where a building, business or region sequesters or offsets as much carbon as it emits.

There are a variety of certification tools and standards for carbon neutrality, including the Commonwealth government’s Climate Active Carbon Neutral Standard.

To achieve certification, an emissions audit is required, and emissions reduction activities undertaken such as energy efficiency and/or uptake of renewables – or ideally both – and then carbon offsets obtained to balance out emissions.

A National Carbon Offset Standard for Buildings and Precincts has been available since 2017. Now called the Climate Active Carbon Neutral Standard for Buildings, it is administered by Climate Active, with certification provided by the NABERS National Administrator or the Green Building Council of Australia.

A spokesperson for Climate Active says currently 13 buildings in Australia have achieved certification.

Carbon offsets

All offsets are not created equal – there are dirt cheap offsets sloshing around the global carbon market from shonky projects in far-flung places. But not only are they scientifically and ethically questionable, they also will not meet the standards required for formal third-party carbon neutral certification.

There’s a range of information available about offset standards, including data from Australian offset provider GreenFleet which plants mixed native conservation areas In Australia. Consultants Energetics and carbon offsets broker Carbon Neutral also give a good overview of the types of offsets available.

One thing many of the certifiers stress is that the best offsets also deliver co-benefits beyond just sequestering carbon, such as improving biodiversity, increasing water quality or catchment protection, generating social benefits, local economic benefits or supporting Indigenous cultural practices and knowledge.

Operational emissions

Most carbon accounting undertaken for the purposes of carbon neutral certification focus on carbon emissions generated by the operation of a building, business or region. It’s not just emissions from energy or fuel use though.

The Greenhouse Gas Protocol defines three “scopes” or categories of carbon emissions.

Scope 1 emissions are direct emissions from “owned or controlled sources” such as a fleet of vehicles, a power plant or a manufacturing plant.

Scope 2 emissions are indirect emissions from the generation of energy used within a building, plant or region – many household energy bills now give a figure for the carbon emissions associated with energy drawn from the grid by the household, for example.

Scope 3 emissions are all the indirect emissions in a business, process or region’s value chain both upstream and downstream. This would include something like methane emissions from waste sent to landfill, or the emissions from energy used to make the widgets that a business procures then retails.

Embodied carbon 

Sustainability leaders are saying embodied energy is the next big challenge.

Basically, almost everything we use, from a smartphone to a building, has embodied carbon.

David Williams from the Planning Institute summed it up in a Spinifex late last year, saying “embodied or upfront carbon refers to the emissions released during the manufacture and transport of building materials, and the construction as well the end-of-life-phases of built assets.”

A paper by Monique Fouche and Robert Crawford notes that as we keep reducing operational emissions, the embodied carbon will start to play a larger role in the lifecycle emissions of the built environment. UNSW researchers say around half of built environment emissions are “hidden” in the lifecycle of delivering the building,

It’s something some of the sustainability front-runners such as GPT are keen to get a grip on early.

A great resource for looking at material impacts, including carbon, is Dick Clarke’s Rethink Building Materials.

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  1. Great summary Willow. Let’s get supply chain dynamics working. Tenants can ask for net zero emission buildings, builders can ask for net zero emission products, everybody wins and the accounting is easy.

    Emphasis on renewable energy as the means to mitigating scope 2 emissions and offsets as a transition strategy as buildings move away from gas and clean up refrigerants and waste.