www.oulu.fi/en/news/study-links-coffee-consumption-metabolic-health-and-sex-hormones

The numbers

First visit

0.187 g CO₂e

Return visit

<0.001 g CO₂e

Hosting

unknown

LCP

532 ms

CLS

n/a

TTFB

42 ms

At 10,000 views a month this page emits about 16.9 kg CO₂e a year, roughly 69 km in an average petrol car. The estimate assumes 75% new and 25% returning visitors, a measured cache reload ratio of 0%, and world-average grid intensity. How we calculate this

1. Enable text compressionsave ~0.053 g/visit (476 kB)High impact · quick fix

   1 text resource (680 kB) are served without gzip/Brotli.

   Enable Brotli (or at least gzip) on the server or CDN for HTML, CSS, JavaScript, JSON and SVG. Typical reduction is ~70%.

   • container_jXu3cj09.js680 kB

   WSG 4.3: Reduce data transfer with compression
2. Reduce JavaScript payloadsave ~0.023 g/visit (204 kB)High impact · moderate effort

   11 scripts total 817 kB on the wire (1.15 MB decoded). Bundles this size usually carry a lot of unused code.

   Split bundles per route, tree-shake dependencies, and audit with a bundle analyzer or coverage profile. A 25% cut is a conservative target for bundles this size.

   • container_jXu3cj09.js680 kB
   • js_-0NJgvzmS1DBFRXhoER5E-6Jpuh2MgyOf52CzBGAf_…54 kB
   • jquery.min.js28 kB
   • js_9OIorBl154A4o_UzMnLKN_eH1aKBvz-u1mLnxofIyg…19 kB
   • en.js13 kB

   WSG 3.2: Minify and remove unused codeWSG 3.3: Modularize bandwidth-heavy components
3. Serve images at the size they displaysave ~0.013 g/visit (118 kB)Medium impact · quick fix

   2 images are encoded at more than twice the pixels the layout shows, even accounting for this viewport's pixel density.

   Generate multiple sizes and let the browser pick with srcset/sizes; a 4000px original behind a 400px slot spends bandwidth no screen displays.

   • kahvi.jpg150 kB
   • KARVI_Excellence_WHITE_logo.png65 kB

   WSG 2.9: Optimize media to reduce resource use
4. Convert and compress imagessave ~0.011 g/visit (98 kB)Medium impact · quick fix

   3 images (217 kB) ship in legacy formats (JPEG/PNG/GIF).

   Serve AVIF (or WebP) with responsive srcset sizes, and re-compress oversized files. AVIF typically halves JPEG weight at the same visual quality.

   • kahvi.jpg150 kB
   • KARVI_Excellence_WHITE_logo.png65 kB
   • certificate-hrex.png2.0 kB

   WSG 2.9: Optimize media to reduce resource use
5. Verify your hosting energyMedium impact · moderate effort

   This host has not published renewable energy evidence with the Green Web Foundation, so its energy source is unknown.

   Choose a provider listed in the Green Web Directory, or ask your current provider to publish evidence (and a carbon.txt). This cuts the data-center share of every single page view.

   • carbon.txtNo carbon.txt found at the site root; publishing one is the lightest first step.

   WSG 4.1: Use sustainable hosting
6. Upgrade compression beyond gzipsave ~0.0041 g/visit (37 kB)Advisory · quick fix

   243 kB of text ships gzip-compressed; Brotli or Zstandard would cut roughly another 15-20%, and browsers without them fall back to gzip automatically.

   Serve precompressed Brotli for static text assets (highest level, compressed at build time) and enable Brotli or zstd for dynamic responses; keep gzip only as the fallback.

   • icons.svg63 kB
   • js_-0NJgvzmS1DBFRXhoER5E-6Jpuh2MgyOf52CzBGAf_…54 kB
   • css_ATVAtTDFLy_HR0v7p2_0CXU5u2MSDJ9j-pIXNtAS6…40 kB
   • jquery.min.js28 kB
   • js_9OIorBl154A4o_UzMnLKN_eH1aKBvz-u1mLnxofIyg…19 kB

   WSG 4.3: Reduce data transfer with compression
7. Optimize web fontssave ~0.0031 g/visit (28 kB)Advisory · quick fix

   2 font files total 93 kB, 2 not in WOFF2.

   Subset fonts to used glyphs, prefer one variable font over multiple weights, serve WOFF2 only, and consider system fonts for UI text.

   • fff-Bold_gdi.woff46 kB
   • fff-Regular_gdi.woff46 kB

   WSG 2.11: Use optimized web typography
8. Upgrade connections to HTTP/2 or HTTP/3Advisory · quick fix

   1 host serves five or more resources over HTTP/1.1, paying per-request connection and header overhead newer protocols eliminate.

   Enable HTTP/2 (or HTTP/3) on the server or move the assets behind a CDN that speaks it; multiplexing makes many small requests nearly free.

   • www.oulu.fi18 requests over http/1.1

   WSG 3.1: Set goals based on performance and energy impact

Where the bytes are

• JavaScript817 kB · 11 req
• Images218 kB · 4 req
• Fonts93 kB · 2 req
• Other63 kB · 1 req
• CSS51 kB · 2 req
• HTML20 kB · 2 req
• Data (fetch)2.9 kB · 1 req
• Data (XHR)691 B · 1 req